Qualitative analysis of research data. Quantitative and qualitative analysis Why is quantitative analysis needed?

Analytical chemistry doing research experimental methods determination of the composition of substances. Determining the composition of substances includes identifying the nature of the components that make up the substance under study and establishing the quantitative relationships of these components.

First install high-quality composition of the object under study, i.e. solve the question of what it consists of, and then proceed to determine the quantitative composition, i.e. find out in what quantitative ratios the detected components are found in the object of study.

Qualitative analysis substances can be carried out using chemical, physical, physicochemical methods.

Chemical methods of analysis are based on the use of characteristic chemical reactions to determine the composition of the analyte.

Chemical analysis of a substance is carried out in two ways: “dry way” or “wet way”. Dry analysis- This chemical reactions, occurring with substances during incandescence, fusion and coloring of the flame.

Wet analysis- These are chemical reactions that occur in electrolyte solutions. The analyzed substance is pre-dissolved in water or other solvents. Depending on the mass or volume of the substance taken for analysis, on the technique used, macro-, semi-micro- and micromethods are distinguished.

Macro method. To carry out the analysis, take 1-2 ml of a solution containing at least 0.1 g of the substance and add at least 1 ml of the reagent solution. The reactions are carried out in a test tube, the precipitate is separated by filtration. The filter cake is washed to remove impurities.

Semi-micromethod. For analysis, 10-20 times less substance is taken (up to 0.01 g). Since this method works with small quantities of a substance, microtubes, watch glasses or slides are used. Centrifugation is used to separate the precipitate from the solution.

Micromethod. When performing an analysis using this method, take one or two drops of the solution, and dry matter - within 0.001 g. Characteristic reactions carried out on a watch glass or porcelain plate.

When carrying out the analysis, the following operations are used: heating and evaporation, sedimentation, centrifugation, checking the completeness of sedimentation, separation of the solution (centrifuge) from the sediment, washing and dissolving the sediment.

Heating solutions can be carried out directly with the flame of a gas burner, on an asbestos grid or in a water bath. A small amount of the solution is heated to a temperature not exceeding 100°C in a water bath, in which the water should boil evenly.

For concentration solutions use a water bath. Evaporation the solution to a dry residue is carried out in porcelain cups or crucibles, heating them on an asbestos mesh. If the dry residue after evaporation needs to be calcined to remove volatile salts, then the crucible is placed on a porcelain triangle and heated with the flame of a gas burner.

Precipitation. The precipitation reaction is carried out in conical flasks or cylindrical test tubes. A precipitating reagent is pipetted into the test solution. The precipitant is taken in excess. The mixture is thoroughly mixed with a glass rod and rubbed against the inner walls of the test tube, this accelerates the process of sediment formation. Precipitation is often carried out from hot solutions.

Centrifugation. The precipitate is separated from the solution by centrifugation using a manual or electric centrifuge. The test tube with the solution and sediment is placed in a sleeve. The centrifuge must be loaded evenly. When rotating quickly centrifugal force throws sediment particles to the bottom and compacts it, and the solution (centrifuge) becomes transparent. The rotation time ranges from 30 s to several minutes.

Checking the completeness of deposition. The test tube is carefully removed from the centrifuge and 1-2 drops of the precipitating reagent are added along the wall to the clear solution. If the solution does not become cloudy, the precipitation is complete. If cloudiness of the solution is observed, then a precipitant is added to the test tube, the contents are mixed, heated and centrifuged again, then the completeness of precipitation is checked again.

Separation of the solution (centrifugate) from the sediment. After making sure that precipitation is complete, separate the solution from the precipitate. The solution is separated from the precipitate using a drop pipette. The pipette is closed with the index finger and carefully removed from the test tube. If the selected solution is needed for analysis, then it is transferred to a clean test tube. For complete separation, the operation is repeated several times. During centrifugation, the precipitate may settle tightly to the bottom of the test tube, then the solution is separated by decantation (carefully drained).

Washing the sediment. The sediment (if it is examined) must be washed well; To do this, a washing liquid is added, most often distilled water. The contents are thoroughly mixed with a glass rod and centrifuged, then the washing liquid is separated. Sometimes in work this operation is repeated 2-3 times.

Dissolution of sediment. To dissolve the precipitate, add a solvent to the test tube, stirring with a glass rod. Often the precipitate is dissolved by heating in a water bath.

For determining quantitative composition substances or products, reactions of neutralization, precipitation, oxidation - reduction, complex formation are used. The amount of a substance can be determined by its mass or the volume of solution spent on interaction with it, as well as by the refractive index of the solution, its electrical conductivity or color intensity, etc.

Based on the amount of substance taken for testing analytical methods quantitative analysis are classified as follows: macroanalysis - 1-10 g of solid substance, 10-100 ml of analyzed solution; semi-microanalysis - 0.05-0.5 solids, 1-10 ml of analyzed solution; microanalysis - 0.001-1-10-4 g of solid substance, 0.1-1 * 10-4 ml of the analyzed solution. In merchandising practice, gravimetric (weight) and titrimetric (volume) methods are often used.

Gravimetric (weight) analysis- one of the methods of quantitative analysis, which allows you to determine the composition of the analyte by measuring mass. Mass measurement (weighing) is performed on an analytical balance with an accuracy of 0.0002 g. This method is often used in food laboratories to determine moisture, ash content, and the content of individual elements or compounds. The analysis can be performed in one of the following ways.

1. Determined component quantitatively (as completely as possible) isolated from the test substance and weighed. This is how the ash content of products is determined. The initial product (sample) weighed on an analytical balance is burned, the resulting ash is brought to a constant mass (calcined until the mass stops changing) and weighed.

The ash content of the product x (%) is calculated using the formula

where B is the mass of calcined ash, g;

A is the initial weight of the product, g.

2. The component being determined is completely removed from the sample of the starting substance and the residue is weighed. This is how the moisture content of the products is determined, while a sample of the starting substance is dried in an oven to constant weight.

The moisture content of the product x (%) is calculated using the formula

where A is the initial sample of the product, g;

B is the mass of the sample after drying, g.

Volumetric analysis- a method of quantitative analysis, where the desired substance is determined by the volume of a reagent with a precisely known concentration spent on the reaction with this substance.

When determining by volumetric method, a reagent with a precisely known concentration is added in small portions (drop by drop) to a known volume of a solution of the analyte until its amount is equivalent to the amount of the analyte. A solution of a reagent with an accurately known concentration is called a titrated, working or standard solution.

The process of slowly adding a titrated solution to a solution of the analyte is called titration. The moment when the amount of the titrated solution is equivalent to the amount of the substance being determined is called the equivalence point or the theoretical end point of the titration. To determine the equivalence point, indicators are used that undergo visible changes near it, expressed in a change in the color of the solution, the appearance of turbidity, or the formation of a precipitate.

The most important conditions for correct performance of volumetric analytical determinations: 1) the ability to accurately measure volumes of solutions; 2) the availability of standard solutions with precisely known concentrations; 3) the ability to accurately determine the moment of completion of the reaction (correct choice of indicator).

Depending on the reaction on which the determination is based, the following types of volumetric method are distinguished:

neutralization method

· oxidation-reduction method

· precipitation and complexation method.

At the core neutralization method lies the reaction of interaction between H + and OH - ions. The method is used to determine acids, bases and salts (that react with acids or bases) in solution. To determine acids, titrated solutions of alkalis KOH or NaOH are used, and to determine bases, solutions of acids HC1, H 2 SO 4 are used.

To determine, for example, the acid content in a solution, a precisely measured volume of an acid solution with a pipette in the presence of an indicator is titrated with an alkali solution of precisely known concentration. The equivalence point is determined by the change in color of the indicator. Based on the volume of alkali consumed for titration, the acid content in the solution is calculated.

Method oxidation - reduction is based on redox reactions occurring between a standard solution and the analyte. If the standard solution contains an oxidizing agent (reducing agent), then the substance to be determined must contain a corresponding reducing agent (oxidizing agent). The oxidation-reduction method is divided, depending on the standard solution used, into the permanganatometry method, the iodometry method, etc.

The basis of the method deposition there are reactions accompanied by precipitation. Unlike the gravimetric method, the sediment is not processed here; the mass of the substance under study is determined by the volume of the reagent consumed for the precipitation reaction.

Every living organism, including bacteria and viruses, has unique genes that are part of the DNA or RNA structure in a certain sequence. During a PCR study, genetic material is copied many times under the influence of DNA polymerase and special temperature cycles.

There are two main polymerase chain reaction methods:

1. The classical method is the isolation of the genetic material of the pathogen by electrophoresis;
2. Real-time PCR.

The technique consists of three main stages:

• Preparation of the test sample;
• DNA amplification;
• Detection (identification) of the genetic material of the suspected pathogen.

To conduct the study, the PCR laboratory must be divided into 3 zones, each stage of the reaction is carried out strictly in the room intended for it. Each zone must be equipped with the necessary equipment, dispensers, consumables, and protective clothing used only in this room.

After registration and labeling of the samples, DNA or RNA of the pathogen is isolated from the test material in the sample preparation room by exposure to a certain temperature and special reagents. Then the process of amplification begins - creating numerous copies of a unique DNA fragment. It consists of 3 main stages:

• DNA denaturation - under the influence of high temperature (95 degrees), the DNA double helix unwinds into 2 chains.
• Primer annealing – special synthetic compounds (primers) that are identical to the genetic information at the ends of the desired fragments are attached to the ends of DNA chains nucleic acids. The temperature required to attach the primer is individual for a particular case and ranges from 50 to 65 degrees Celsius.
• Using the enzyme DNA polymerase, a similar DNA section (amplicon) is completed between two primers at 70–72 degrees. As " building material» special substances are used that are added to the test tube.

Amplification cycles are repeated several times, therefore, the isolated DNA is copied many times, which simplifies the process of its identification. Identification can be carried out visually after electrophoresis of amplification products in an agarose gel, or automatically using the real-time technique.

When researching using the PCR method in “real time”, amplification and detection occur simultaneously in special devices. This method is the most preferable, since the study is carried out in closed test tubes, reducing the risk of contamination and, consequently, the issuance of false positive results.

Pros and cons of the method

• The study takes only a few hours, in contrast to lengthy classical microbiological methods;
• High specificity from 95% to 100%, because the required DNA fragment is unique for each specific microorganism;
• The method is highly sensitive; a pathogen can be detected even if it is represented by only one cell in the test sample;
• The pathogen can be identified both qualitatively and quantitative method. This is very important when isolating opportunistic microorganisms that do not cause disease in small quantities;
• Possibility to determine the genotype of the pathogen (hepatitis C, HIV infection). This is necessary for rational treatment and prognosis of possible complications;
• The ability to identify a genetic predisposition to the disease, thereby preventing its development;
• Almost any source of infection can be identified; modern techniques also make it possible to identify the total microflora in the test sample, for example, the vaginal biocenosis.

• The possibility of obtaining both a false-positive and a false-negative sample in case of non-compliance with the rules of sample collection or errors during the study;
• High cost of analysis.

Application

Almost any sample can be examined using the PCR method (blood, urine, cerebrospinal fluid, scrapings from the cervical canal and urethra, hair follicles, semen, etc.). This technique is widely used to diagnose STDs (gonorrhea, chlamydia, ureaplasmosis, mycoplasmosis, trichomoniasis). With its help, you can identify pathogens of tuberculosis, diphtheria, pneumonia, viral hepatitis, HIV infection, toxoplasmosis, cytomegalovirus and herpetic infections, salmonellosis, etc.

Polymerase chain reaction is used to establish paternity by comparing the DNA of the parent and child, identifying genetic abnormalities and the body's hereditary predisposition to various diseases.

Preparing for the test

• It is recommended to donate blood strictly on an empty stomach.
• Before taking a smear from the urethra or cervical canal, you should abstain from sexual activity for three days; the test must be taken no earlier than a month after the end of the course of antibiotic therapy, otherwise the result may be false positive. The PCR method detects the DNA of even a dead pathogen, so it is better to conduct the study after complete cell renewal.
• Urine should be collected in a sterile container.

The answer will most often be ready in a couple of days, depending on the capabilities of the laboratory.

Decoding the results

When using a qualitative methodology, there can only be 2 answer options: positive or negative. A positive result indicates the presence of the isolated microorganism in the sample, a negative result indicates its absence.

The quantitative result must be assessed by the attending physician; an individual approach is applied in each specific case. The specialist, taking into account the received answer, decides on the need for treatment, dosage of drugs, and clarifies the form and stage of the disease.

When determining the genetic profile (predisposition to thrombophilia, breast cancer), after deciphering the result, the doctor can assess the degree of risk of developing the disease, as well as prescribe a special diet and preventive measures.

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Polymerase chain reaction - information for patients

Polymerase chain reaction (PCR) is a complex laboratory method widely used in medicine and other branches of science. At one time, PCR diagnostics became a big breakthrough in science. We can say that this is one of the most important discoveries of the 20th century in medicine. For the discovery of the method, Keri Mullis, a biochemist, received the Nobel Prize in 1993.

For a long time, infections have exacted a bitter toll from humanity. The plague alone claimed hundreds of thousands of lives in the Middle Ages. In the successful fight against epidemics, accurate and timely diagnosis is important.

PCR tests are usually carried out in a laboratory at the clinic. Despite the fact that the PCR test for infection is quite expensive, the price is compensated by its high accuracy. To establish an accurate diagnosis, it is enough to do the analysis once. If other methods are used, additional or repeat tests may be required.

How is testing for infectious diseases performed?

The most common methods used to diagnose infections are serological and cultural methods. In the first case, antibodies to the infectious agent are determined in the blood serum. In the second case, biological material obtained from a sick person is used to inoculate a special environment favorable for the growth of pathogen colonies. In both cases, diagnosis can take days or even weeks.

PCR examination can be carried out with any biological materials obtained from a sick person. Blood and other biological, physiological and pathological fluids and media can serve as samples. You can do PCR of urine or stool.

Most often, the PCR method is used to determine viral and atypical infections, since they may not be amenable to conventional diagnosis due to the characteristics of the pathological process they cause. In order to diagnose these infections, time is required during which the body begins to produce antibodies, which are determined by serological methods. However, in some cases this is unacceptable.

Using PCR, the human immunodeficiency virus can be determined within days or weeks, as accurately as possible, without the seronegative window period characteristic of other methods. (The seronegative window is the period from the moment of infection during which the body has not yet begun to produce a sufficient amount of antibodies for detection).

The in vitro PCR method means laboratory determination of infection in samples isolated from the patient.

To carry out a polymerase chain reaction, a set of special reagents is required.

The test material is added to test tubes with reagents. The tubes are placed in a special device - a PCR amplifier. It serves to amplify (increase the number) of the desired DNA or RNA fragments. The PCR amplifier runs in cyclic mode. Each cycle, if the DNA or RNA sequence of the pathogen is present in the samples, copies of fragments of these nucleic acids accumulate in the solution. Both the presence of the pathogen and its quantity in the samples can be determined.

Types of PCR

Analysis by PCR method - qualitative gives the following result:

• PCR - negative, the desired pathogen was not detected in the samples;
• PCR is positive; sequences characteristic of a particular pathogen were found in the samples.

When the PCR result is positive, this indicates with 95% accuracy the presence of a diagnosable infection. The accuracy of PCR kits used for diagnostics reaches 100%.

5% of erroneous results usually depend on the human factor. Thus, violations of the rules for storing reagents and research techniques can significantly reduce the accuracy of analyzes.

Quantitative PCR analysis determines the concept of viral load. In this case, it is possible to determine how many sets of pathogen DNA were contained in the samples obtained from the patient. The more, the more severe the infection. You can also determine the success of treatment by reducing the viral load.

Submission of biomaterial for PCR

PCR tests are carried out in the clinic, usually in the morning. During your visit to the doctor, you will be told what you need to donate: blood, urine, smear or scraping. PCR is capable of identifying pathogens regardless of the degree of contamination of the material.

In theory, for a positive analysis, the presence of only one pathogen in the samples is sufficient. In practice, they are trying to create more favorable conditions. There are some rules for this:

• if you are taking a smear or scraping from the genitals, you should abstain from sexual intercourse 3 days before the test;
• You should not wash yourself or douche with antibacterial agents on the eve of the test;
• 3 hours before taking a smear from the urethra, you should be patient and not urinate.

In the case where a patient donates blood, these rules may not be followed.

Research results

PCR results are usually ready within 24 hours after testing. Qualitative analysis looks simple. PCR decoding is not required, since usually the pathogen is indicated in the first column, and the result in the second. For example, like this:

(PCR) Ureaplasma urealiticum

(PCR) Herpes simplex

The method indicated in parentheses is PCR. Making an interpretation is not difficult. The patient from the example was diagnosed with cytomegalovirus (CMV) and herpes using a qualitative PCR method. Ureaplasma and chlamydia: no infectious agents were detected.

Quantitative analysis gives a numerical result, usually in IU/ml. This means that in 1 ml of the test sample a certain number of copies of DNA or RNA of the pathogen was detected, in international units. Depending on the size, the severity of the infection is determined. Usually, blood is tested to determine the viral load, since during illness viruses circulate freely in the blood.

Where can I get PCR done?

It is important to get tested in a well-established clinic. Although the method is very accurate, its results are affected by adherence to the study protocol. You should not look for a clinic based on the results of queries in a search engine, such as: PCR Moscow, where to do it or PCR Stavropol clinic. As a rule, your doctor recommends where it is best to do a PCR test.

If the PCR result is positive, it is necessary to repeat the test in another laboratory. This will eliminate human error.

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Diagnosis of hepatitis C using PCR testing

Polymerase chain reaction (PCR) is increasingly being used in clinical practice to determine the causes of various viral diseases, including the diagnosis of viral hepatitis C.

Advice from hepatologists

In 2012, there was a breakthrough in the treatment of hepatitis C. New direct-acting antiviral drugs were developed, which with a 97% probability of completely eliminating the disease. From this point on, hepatitis C is officially considered a completely curable disease in the medical community. In the Russian Federation and CIS countries, drugs are represented by the brands sofosbuvir, daclatasvir and ledipasvir. There are a lot of fakes on the market at the moment. Medicines of proper quality can only be purchased from companies that have licenses and appropriate documentation.

PCR in its various modifications is actively used for its diagnosis. Using PCR for hepatitis C, it is possible to determine the presence of hepatitis C virus RNA in the patient’s blood and accurately make a diagnosis.

Analysis Variations

The PCR technique became available to doctors several decades ago. It is based on multiple copies of a certain fragment of viral or bacterial RNA or DNA, followed by detection (recognition of this fragment) in the patient’s blood serum.

At the same time, there are two fundamentally different methods of PCR research: quantitative and qualitative.

The qualitative method only allows us to answer the question: is there genetic material of a certain virus in the biological material (blood serum, saliva, seminal fluid, etc.)?

The quantitative method, in turn, makes it possible to determine the amount of this genetic material, which is necessary in some cases to determine the stage of the disease or assess the effectiveness of therapy.

Qualitative PCR option for disease

The use of a qualitative version of PCR analysis for this disease makes it possible to detect the presence of hepatitis C viral RNA in biological fluids (blood serum, saliva, etc.) of the patient. In this case, the result of the analysis can only be of two types: positive or negative. In this case, its correct decoding is very important.

• a positive result when determining hepatitis C viral RNA tells the doctor that the biological fluid being tested contains RNA of this virus. Accordingly, the patient is infected with it, and, therefore, a diagnosis of viral hepatitis C is possible. However, it is always worth remembering the possibility of false positive test results;
• a negative result of PCR analysis indicates the absence of hepatitis C virus RNA in the biological fluid being tested, or the content of RNA molecules in the test fluid was too low and was below the sensitivity limit of the PCR method. A negative test result may not always indicate the absence of the virus in the blood. The possibility of false negative test results should always be considered by the attending physician.

With the development of an acute form of hepatitis C disease, conducting a high-quality PCR study makes it possible to establish the fact of the disease within 1-3 weeks after the virus enters the human body.

False negative results may result from:

• penetration of polluting substances into biological material (blood);
• the use of Heparin to prevent blood clotting in vitro or its use by the patient;
• penetration into the test material of substances from environment, blocking enzymes used in PCR.

Quantitative PCR option

The use of quantitative PCR analysis makes it possible to determine not only the very presence of the virus in the blood, but also the number of viral particles in any biological fluid (the so-called viral load). Using this type of PCR, you can determine the number of copies of hepatitis C virus RNA that circulate in a certain volume.

Result of this type PCR is expressed as numerical values, where the unit of measurement is international units per milliliter - IU/ml.

This type of PCR diagnosis is used on certain days of treatment for viral hepatitis C. The first determination of the viral load occurs when a sick person is admitted to the hospital. Subsequently, the analysis is carried out at the 1st, 4th, 12th and 24th weeks from the start of drug use. Already in the 12th week you can tell whether the therapy is effective or not.

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There is no need to specially prepare the patient for the study. It is recommended not to smoke on the day of the test. Blood from a vein is used as the test material.

After quantitative PCR has been carried out, it is necessary to decipher the results obtained. The concept of “norm” does not exist in such cases. To decipher, a specially developed gradation of indicators is used:

• test result: not detected - hepatitis C viral RNA was not detected in the patient’s venous blood (negative result), or it is contained in a very low amount, which does not allow the method to determine it (<40 ME/мл – порог чувствительности количественного ПЦР);
• research result:<8*10 5 МE/мл – положительный результат теста. Такой уровень вирусной нагрузки очень низкий. Является показателем эффективности терапии и благополучного течения заболевания;
• test result: >8*10 5 IU/ml – positive test result. The load level is very high. Poor prognosis for the course of the disease and the need for correction or replacement of medications used.

It is important to remember that the resulting level of viral load does not reflect the severity of the pathology and the degree of liver destruction. For this, there are other methods of biochemical research. To correctly select treatment methods, it is necessary to know the genotype of the hepatitis C virus.

1. A high level of concentration of viral particles in biological fluids, and especially in the blood, is associated with a high risk of transmission of the virus through sexual contact or during pregnancy from mother to fetus.
2. The number of viral particles is a reflection of the effectiveness of the drugs used and allows for rational selection of drugs and doses used.

Ultrasensitive PCR diagnostic method

Today, you can undergo the so-called ultra PCR to determine the hepatitis C virus. This method is completely called PCR with hybridization-fluorescence research in real time.

When is ultra PCR indicated:

1. In cases of suspected viral hepatitis C in patients with latent forms of the disease.
2. In cases where the patient has antibodies to the hepatitis C virus, but not confirmed by PCR diagnostics.
3. To assess the effectiveness of the treatment and confirm the fact of recovery.
4. As a screening technique for early detection of disease in people in the population.

To conduct the study, as a rule, the patient's venous blood is used. The sensitivity of the ultra method is less than 10 IU/l, which is several times higher than that of standard quantitative and qualitative PCR diagnostic options. Ultra PCR is prescribed by an infectious disease specialist or hepatologist.

The decisive stage in making a diagnosis and evaluating treatment is the correct interpretation of the results obtained using the ultra PCR method. It is always worth remembering that there is a small chance of getting false negatives and false positives.

To eliminate such situations, it is necessary to prevent contamination of blood samples and laboratory materials. By using ultra PCR it is possible to avoid situations that lead to false negative results and thereby complicate diagnosis.

Judging by the fact that you are reading these lines now, victory in the fight against Hepatitis C is not yet on your side.

And have you already taken toxic drugs that had a lot of side effects? This is understandable, because ignoring the disease can lead to serious consequences. Fatigue, weight loss, nausea and vomiting, yellowish or grayish skin tone, bitterness in the mouth, body and joint aches. Are all these symptoms familiar to you firsthand?

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What is the difference between qualitative and quantitative PCR?

View full version: PCR

Please tell me which PCR smear test for STDs is more informative: qualitative or semi-quantitative? How are they different from each other?

In general, there are 2 types of PCR - qualitative (yes/no) and quantitative. Quantitative requires different equipment, much more expensive, and is used mainly for HIV and hepatitis.

Semi-quantitative analysis, in a certain sense, is an inadequate surrogate for quantitative analysis; it is not necessary to do it:

This is not a quantitative analysis

It is usually more expensive

When diagnosing an STD, the number of microorganisms does not matter.

This is usually a separate study.

Special media are used, usually imported, most often MYCOPLASMA DUO + ​​antibiogram SIR (BIORAD, France) or MYCOPLASMA IST (BioMerrier), but it is more expensive. The cost of detection is about $10 for both infections.

It makes sense to do PCR only in the sense of diagnosing mycoplasmas that are not detected by culture - M.genitalium.

It is also possible as a cheap option for identifying all mycoplasmas in general - usually called Mycoplasma spp. (i.e. all species of the genus Mycoplasma). However, non-pathogenic ones are also determined, so a negative answer is of great value.

What is the name of the diagnosis if one elementary or reticular body of the main forms of chlamydia is detected? The question is similar regarding the detection of one or more pairs of gonococci, as well as one Trichomonas cell. Thank you for your attention and the discussion you started. Best regards, Vladimir.

How are you going to find ONE elemental or reticular body?

With light microscopy, this is impossible; with immunofluorescence, there are criteria for issuing a response - usually these are 5-10 objects with a characteristic glow, depending on the set.

With PCR and ELISA for antigens, the question is generally inadequate.

The sensitivity of most Russian PCR kits is about 1000 genocopies per ml of sample.

The answer is similar - how to do this?

Regarding Trichomonas, options are possible, but still ONE cell is casuistry, and you can always check the result using another method, the same PCR, by the way.

For gonorrhea, this is impossible - using a Gram-stained smear, the diagnosis of gonorrhea can only be made in acute gonorrhea in men (and in America this is also only a presumptive diagnosis), and one pair of gonococci can be found VERY RARE. All other cases are “Gram-negative intracellular diplococci.”

When sowing, you get a COLONY of gonococci, which you must identify (now this is not a problem).

For PCR, see above.

Gonococcus is determined by microscopy of Gram-stained smears;

Trichomonas microscopy of a native smear;

Chlamydia - PCR or culture on special media;

Mycoplasmas - inoculated on special media

So? It's enough? Do antibody levels play a role in diagnosing STDs?

Bacterial culture with subsequent identification of colonies using modern kits for differentiating Neisseria. Unfortunately, this is rarely done anywhere. In HPT, as a rule, identification on sugars is not carried out, although it should be.

Bacterioscopy (acute gonorrhea in men)

Microscopy of the native drug and its modifications

Culture for Trichomonas

Microscopy of stained smears (use only if typical forms are detected, and not “scraps of Trichomonas”)

Sowing on a cage. cultures or embryos (difficult)

The only possible benefit can be assumed for ascending chlamydial infection or Reiter's syndrome.

Often in the CIS they lead to multiple treatments “until the titer disappears”

As a method of monitoring cure - absolutely not!

I think STD screening will switch to nucleic acid amplification methods (the same PCR)

For chlamydia this is already the case, for gonorrhea this is increasingly the case.

Compared to a background or virological study, PCR is simpler and faster for both the clinician and the laboratory, and therefore more reliable.

The background study will remain a reference method. This is my forecast.

Do you think there is at least one adult person on Earth who has “encountered” one or another subspecies of chlamydia more than once during his life? What, however, with most of the other potentially pathogenic microflora? In the overwhelming majority of cases, such meetings (usually in low titers) end tragically for this microflora. 🙂 Much less often as a carrier (usually temporary), and even less often as a disease.

And the second question, what do you think: why, over many millennia of human coexistence with at least the same Chlamydia trachomatis, when chlamydia (this is not a reservation, because they are often treated specifically for the bacterial agent that was detected using PCR 😎) They just didn’t treat it, but, in general, their coexistence was not known, did not everyone get chlamydia? After all, in the history of mankind there were quite a few periods when polygamous sexual relationships were the norm.

This is often where “persistence” comes from. Venereologists refuse to believe the results - “you don’t find anything, here in our smears.” (Interestingly, the KVD statistics and ours for Trichomonas and gonorrhea are approximately the same. Well, where is “what’s in the smears”?) And so on, and etc.

But let’s not forget the question from dear ksena: “Good afternoon!

Please tell me which PCR smear test for STDs is more informative: qualitative or semi-quantitative? How are they different from each other?"

This question, in my opinion, is from the area of ​​​​interest in human knowledge. And knowledge has no boundaries. Over time, the question of pathological molecules (prion proteins), then about the tension in torsion fields at the atomic level, etc., will be interesting, and then attention will turn to the macrocosm. There will be questions from astrology about the influence of planets on our health. His Majesty EXPERIENCE. But for this question I am very grateful. All the best, with respect to everyone present, Vladimir.

But let’s not forget the question from dear ksena: “Good afternoon!

Please tell me which PCR smear test for STDs is more informative: qualitative or semi-quantitative? How are they different from each other?"

Hello, dear readers!
We are pleased to welcome you to educational service and we hope that we can answer all your questions. Have you visited our website to find out what qualitative analysis and qualitative analysis are? What are the similarities and differences? I'm waiting for your opinion.

At the beginning, I would like to note that the subject of psychology is very complex and for the deepest understanding of it, it is necessary, first of all, to determine what lies at the foundation.

PSYCHOLOGY is a science that studies the patterns of emergence, development, and functioning of the human psyche, as well as groups of people. Once we have determined what the science of psychology studies, we can move on to consider this issue more specifically.

It is worth noting that the main concepts that we will encounter in the course of our discussion on this topic are: PSYCHOLOGY, ANALYSIS, QUANTITATIVE, QUALITATIVE, PERSONALITY. And now, after clarifying the fundamental concepts, we can move on to a specific consideration of your question.

First, let's look at what the term “ANALYSIS” means? Analysis is a research method characterized by the isolation and study of individual parts of the objects of study. After we have determined what is commonly called and considered analysis. Let's move on to consider your question in more detail. What is quantitative analysis? What are its main features? Quantitative Analysis is a set of procedures, methods for describing and transforming research data based on the use of mathematical and static apparatus. It is worth noting that this analysis implies the ability to treat the results as numbers - the use of certain calculation methods. Now let's look more specifically at what is qualitative analysis? Qualitative analysis h is a set of procedures and methods for describing research data based on theoretical conclusions and generalizations, individual experience, intuition, and logical inference methods. In the course of this analysis, the causes of the occurrence of this or that psychological phenomenon are revealed, its essential properties are revealed, development trends are established, and the contradictions in functioning are determined.

It can be added that each of these analyzes plays a certain role in psychology and, under some circumstances, each has its own advantages. This concludes our lesson. I believe that you have learned what properties imagination has in psychology. If anything remains unclear from this topic, you can always ask your question on our website.
We wish you good luck and success in your work!

Already in the course of the study, one can assume about its results, but usually these conclusions are considered preliminary, and more reliable and thorough data can only be obtained as a result of a thorough analysis.

Data analysis in social work is about integrating all the information collected and bringing it into a form suitable for explanation.

Methods for analyzing social information can be divided into two large classes in accordance with the form in which this information is presented:

- qualitative methods focused on the analysis of information presented mainly in verbal form.

- quantitative methods are mathematical in nature and represent processing techniques digital information.

Qualitative analysis is a precondition for the use of quantitative methods; it is aimed at identifying the internal structure of the data, that is, at clarifying those categories that are used to describe the sphere of reality being studied. At this stage, the final determination of the parameters (variables) necessary for a comprehensive description occurs. When there are clear descriptive categories, it is easy to move on to the simplest measurement procedure - counting. For example, if you identify a group of people who need certain help, you can calculate the number of such people in a given microdistrict.

In a qualitative analysis, there is a need to produce information compression, that is, obtain the data in a more compact form.

The main method of information compression is coding - the process of analyzing qualitative information, which includes the identification of semantic segments text or real behavior, their categorization (naming) and reorganization.

To do this, find and mark in the text itself keywords, that is, those words and expressions that carry the main semantic load directly indicate the content of the text as a whole or its individual fragment. Different types of highlighting are used: underlining with one or two lines, color marking, making notes in the margins, which can be in the nature of both additional icons and comments. For example, you can highlight those fragments where the client talks about himself. On the other hand, you can highlight everything that concerns his health; you can separate those problems that the client is able to solve himself, and those problems for which he needs outside help.

Fragments of similar content are marked in a similar way. This allows them to be easily identified and, if necessary, collected together. Then the selected fragments are searched using different headings. By analyzing the text, you can compare its individual fragments with each other, identifying similarities and differences.

The material processed in this way becomes easily visible. The main points come to the fore, as if rising above the mass of details. It becomes possible to analyze the relationships between them, identify their general structure and, on this basis, put forward some explanatory hypotheses.

When several objects are studied simultaneously (at least two) and when comparison in order to detect similarities and differences becomes the main method of analysis, the comparative method is used. The number of objects studied here is small (most often two or three), and each of them is studied in sufficient depth and comprehensively.

It is necessary to find a form of data presentation that is most convenient for analysis. The main technique here is schematization. A scheme always simplifies real relationships and coarsens the true picture. In this sense, schematization of relationships is also a compression of information. But it also involves finding a visual and easily visible form of presenting information. This purpose is served by combining data into tables or diagrams.

For ease of comparison, the material is summarized in tables. The general structure of the table is as follows: each cell represents the intersection of a row and a column. The table is convenient because it can include both quantitative and qualitative data. The point of the table is that it can be glanced at. Therefore, usually the table should fit on one sheet. The pivot table used for analysis is often drawn on a large sheet of paper. But a large table can always be divided into several parts, that is, several tables can be made from it. Most often, a row corresponds to one case, and the columns represent its various aspects (features).

Another method of concise and visual presentation of information is diagrams. There are different types of diagrams, but almost all of them are structural diagrams, in which elements are depicted with conventional figures (rectangles or ovals), and connections between them are depicted with lines or arrows. For example, using a diagram is convenient to represent the structure of any organization. Its elements are people, or more precisely, positions. If the organization is large, then larger structural elements—divisions—are selected as elements. Using the diagram, it is easy to imagine the hierarchy of relationships (the system of subordination): senior positions are located higher on the diagram, and junior ones are lower. The lines connecting the elements indicate exactly who is directly subordinate to whom.

Representation in the form of diagrams can also be used to identify the logical structure of events or text. In this case, a semantic analysis is first carried out and key events or components are outlined, and then they are presented in graphical form so that the connection between them becomes as clear as possible. It is clear that schematization leads to a coarsening of the picture due to the omission of many details. However, information is compressed and converted into a form convenient for perception and memorization.

Thus, the main techniques of qualitative analysis are coding and visual presentation of information.

Quantitative analysis includes methods for statistical description of a sample and methods for statistical inference (testing statistical hypotheses).

Quantitative (statistical) methods of analysis are widely used in scientific research in general and in the social sciences in particular. Sociologists resort to statistical methods to process the results of mass public opinion polls. Psychologists use the apparatus of mathematical statistics to create reliable diagnostic tools - tests.

All methods of quantitative analysis are usually divided into two large groups. Methods of statistical description are aimed at obtaining a quantitative characteristic of the data obtained in a specific study. Statistical inference methods allow one to correctly extend the results obtained in a specific study to the entire phenomenon as such, and to draw conclusions of a general nature. Statistical methods make it possible to identify consistent trends and build on this basis theories designed to explain them.

Science always deals with the diversity of reality, but it sees its task in discovering the order of things, some stability within the observed diversity. Statistics provide convenient methods for such analysis.

To use statistics, two basic conditions are required:

a) it is necessary to have data about a group (sample) of people;

b) this data must be presented in a formalized (codified) form.

It is necessary to take into account possible sampling error, since only individual respondents are taken for the study; there is no guarantee that they are typical representatives of the social group as a whole. Sampling error depends on two factors: the sample size and the degree of variation of the characteristic that interests the researcher. The larger the sample, the less likely it is that it will include individuals with extreme values ​​of the variable under study. On the other hand, the lower the degree of variation of a characteristic, the closer each value will be in general to the true mean. Knowing the sample size and obtaining a measure of the dispersion of observations, it is not difficult to derive an indicator called standard error of the mean. It gives the interval within which the true population mean should lie.

Statistical inference is the process of testing hypotheses. Moreover, the initial assumption is always made that the observed differences are random in nature, that is, the sample belongs to the same general population. In statistics, this assumption is called null hypothesis.

Methodology for preparing final (qualifying) work, requirements for its content and format

The final (qualifying) work completes the training of a social work specialist at a university and shows his readiness to solve theoretical and practical problems.

The final (qualifying) work must be an independent, complete development, in which current problems of social work are analyzed, the content and technologies for solving these problems are revealed not only in theoretical, but also in practical terms at the local and regional levels. Any final (qualifying) work in social work should be a kind of social project.

The final (qualifying) work must indicate that the author has deep and comprehensive knowledge of the object and subject of research, the ability to conduct independent scientific research using the knowledge and skills acquired during the development of the main educational program;

The final (qualifying) thesis must contain a rationale for the choice of research topic, a review of published specialized literature on this issue, a presentation of the research results, specific conclusions and proposals.

The final (qualifying) work must demonstrate the author’s level of mastery of scientific research methods and scientific language, his ability to present the material briefly, logically and reasonably.

The final (qualifying) work should not mechanically repeat the graduate’s academic work (coursework, abstracts, etc.).

Conclusions, proposals and recommendations on the problems under study, put forward by the author to the bodies, organizations, institutions and services of social protection of the population, must be specific, have practical and theoretical value, and have elements of novelty.

Objectives of the thesis:

Systematization, consolidation and expansion of theoretical and practical knowledge in social work, their application in solving specific practical problems;

Development of independent work skills;

Mastering the methodology of research, generalization and logical presentation of material.

In the thesis the student must show:

Solid theoretical knowledge on the chosen topic, problematic presentation of theoretical material;

Ability to study and summarize general and specialized literature on the topic, solve practical problems, draw conclusions and suggestions;

Skills in analysis and calculations, experimentation, computer skills;

Ability to competently apply methods for assessing the social effectiveness of proposed activities.

The thesis has a clear composition: introduction, main part, consisting of several chapters, and conclusion.

The introduction indicates the topic and purpose of the thesis, substantiates the relevance of the research, its theoretical and practical significance, and names the main research methods. It provides the rationale for addressing this topic, its relevance at the moment, the significance, purpose and content of the tasks set, the object and subject of the research are formulated, and it is reported what the theoretical significance and practical value of the results obtained are.

Topics of final (qualifying) works are approved by the graduating departments. The topic must correspond to the specialty; when formulating it, it is advisable to take into account the scientific directions that have developed in the department and the possibility of providing students with qualified scientific guidance. It is desirable that the topics be relevant and have novelty, theoretical and practical significance. When formulating a topic, one must take into account the presence or absence of literature and practical materials, the student’s own work on the topic (term papers, scientific reports, etc.), the student’s interest in the chosen topic, and the student’s ability to conduct the necessary research.

Consequently, the introduction is a fairly important part of the thesis, since it predetermines the further development of the topic and contains the necessary qualification characteristics.

The relevance of the topic, importance, significance at the present time, modernity, topicality is a prerequisite for any scientific work. Justification of relevance is the initial stage of any research, characterizing the student’s professional training in how he knows how to choose a topic, formulate it, how correctly he understands it and evaluates it from the point of view of modernity, its scientific or practical significance. Coverage of relevance should not be wordy. It is enough to show the essence of the problem, to determine where the border between knowledge and ignorance about the subject of research lies.

From the formulation of the scientific problem and evidence that its part, which is the object of study of this work, has not yet received sufficient development and coverage in the scientific literature, it is logical to move on to the formulation of the purpose of the research being undertaken, as well as pointing out specific tasks that need to be solved in accordance with this purpose. Purpose of the study- what the graduate student strives for in his thesis, what he is going to accomplish, establish, why he took up the development of this topic. In accordance with the given goal, the student will have to formulate specific research objectives as certain stages of research that must be completed to achieve the goal.

In addition to the above, a mandatory element of the introduction is the formulation of the object and subject of the study, where an object is a process or phenomenon that generates a problem situation and is chosen for research, and item- something that is within the boundaries of the object. The object and subject of research are related to each other as general and specific. It is on the subject of the research that the thesis student’s main attention should be directed, since it is the subject of the research that determines the topic of the work indicated on the title page.

An obligatory element of the introduction of a scientific work is also an indication of research methods, which serve as a tool in obtaining factual material, being a necessary condition for achieving the goal set in such work.

The introduction describes other elements of the scientific process. These include, in particular, an indication of what specific material the work itself was performed on. It also provides a description of the main sources of information (official, scientific, literary, bibliographic), and also indicates the methodological basis of the study.

Main part consists of several chapters, which, in turn, are divided into paragraphs. This compositional part outlines the main theoretical principles of the thesis, analyzes the factual material, and provides statistical data. Possible illustrative material can be presented here or included in the appendix.

In the main part of the work, the student reveals the methodology and methodology of the research, using for this purpose the following methods: observation, comparison, analysis and synthesis, induction and deduction, theoretical modeling, ascent from the abstract to the concrete, and vice versa.

The content of the chapters of the main part must correspond exactly to the topic of the work and fully disclose it. The conclusions drawn by the graduate student in the study must be consistent, reasoned, and scientifically substantiated. In this case, argumentation is understood as a logical process, the essence of which is that it substantiates the truth of the expressed judgment with the help of other judgments, examples, and arguments.

Conclusion contains conclusions on the thesis. Conclusions should reflect the main content of the work, be accurate and concise. They should not be replaced by a mechanical summation of conclusions at the end of chapters that present a brief summary, but contain something new that constitutes the final results of the study. It is here that the knowledge that is new in relation to the original knowledge is contained. It is this that is brought up for discussion and evaluation by the state commission and the public in the process of defending the thesis.

If the work had practical significance, the conclusions should contain indications of where and how they can be applied in social work practice. In some cases, it becomes necessary to indicate ways to continue researching a topic, those tasks that future researchers will have to solve first. The work is completed with a list of normative materials used and a list of references used.

Auxiliary or additional materials that clutter the text of the main part of the work are placed in the appendix. The content of applications can be quite diverse. These, for example, can be copies of original documents (Charter, Regulations, Instructions, reports, plans, etc.), individual excerpts from instructions and rules, unpublished texts, etc. In form they can be text, tables, graphs , cards.

The appendices cannot include a bibliographic list of used literature, auxiliary indexes of all types, reference comments and notes, which are not appendices to the main text, but elements of the reference and accompanying apparatus of the work that help to use its main text.

The final qualifying work is submitted to the department in printed form. The approximate amount of work should be 2-2.5 p.l. (50-60 pages of typewritten text). Field boundaries: left - 3.5 cm; on the right - 1.5 cm, on top and bottom - 2.5 cm. Computer typing is carried out in the text version of Microsoft Word (interval 1-1.5 according to the multiplier, 12-14 font Times New Roman).

All pages of the work, including pages with tables and diagrams, are numbered sequentially in Arabic numerals, located, as a rule, above the middle of the text.

The title page of the thesis includes the full name of the organization in which the work was performed, the name of the department, the title of the essay, the code and name of the specialty, the surname and initials of the performer, surname, initials, scientific degree (position, title) of the supervisor, city and year of writing.

The titles of chapters and paragraphs are indicated in the same sequence and in the same wording in which they are given in the text of the work.

The text of the main part of the work is divided into chapters, sections, subsections, paragraphs, paragraphs.

The thesis, prepared in accordance with the requirements, must be submitted to the graduating department no later than 14 days before the defense period. The terms of the pre-defense and the terms of defense of the thesis are established by the graduating department.

Analysis of a substance can be carried out to establish its qualitative or quantitative composition. In accordance with this, a distinction is made between qualitative and quantitative analysis.

Qualitative analysis makes it possible to establish what chemical elements the analyzed substance consists of and what ions, groups of atoms or molecules are included in its composition. When studying the composition of an unknown substance, a qualitative analysis always precedes a quantitative one, since the choice of a method for quantitative determination of the constituent parts of the analyzed substance depends on the data obtained from its qualitative analysis.

Qualitative chemical analysis is mostly based on the transformation of the analyte into some new compound that has characteristic properties: color, a certain physical state, crystalline or amorphous structure, specific odor, etc. The chemical transformation that occurs in this case is called a qualitative analytical reaction , and the substances that cause this transformation are called reagents (reagents).

For example, to discover -ions in a solution, the analyzed solution is first acidified with hydrochloric acid, and then a solution of potassium hexacyanoferrate (II) is added. In the presence of a blue precipitate of iron(II) hexacyanoferrate (Prussian blue):

Another example of qualitative chemical analysis is the detection of ammonium salts by heating the analyte with an aqueous solution of sodium hydroxide. Ammonium ions in the presence of -ions form ammonia, which is recognized by its smell or by the blueness of wet red litmus paper:

In the examples given, solutions of potassium hexacyanoferrate (II) and sodium hydroxide are, respectively, reagents for and -ions.

When analyzing a mixture of several substances with similar chemical properties, they are first separated and only then are characteristic reactions carried out on individual substances (or ions), so qualitative analysis covers not only individual reactions for detecting ions, but also methods for their separation.

Quantitative analysis makes it possible to establish quantitative relationships between the constituent parts of a given compound or mixture of substances. In contrast to qualitative analysis, quantitative analysis makes it possible to determine the content of individual components of the analyte or the total content of the analyte in the product under study.

Methods of qualitative and quantitative analysis that make it possible to determine the content of individual elements in the analyzed substance are called elemental analysis; functional groups - functional analysis; individual chemical compounds characterized by a certain molecular weight - molecular analysis.

A set of various chemical, physical and physicochemical methods for separating and determining individual structural (phase) components of heterogeneous! systems that differ in properties and physical structure and are limited from each other by interfaces are called phase analysis.