Chemical toxicological study. Chemical-toxicological study of urine: what is it and how is it carried out

Toxicological testing is done for many reasons. A common task is to confirm or rule out exposure to a toxic substance as suggested by interview and physical examination data. The result of laboratory analysis is the most reliable basis for the diagnosis and often makes it possible to refuse other additional studies. In more than half of the cases, toxicological testing can significantly clarify the diagnosis. Sometimes the diagnosis is made mainly on the basis of laboratory data, especially in cases of poisoning with substances whose toxic effect does not appear immediately (for example, paracetamol), or when poisoning with several substances at once, when different symptoms overlap one another.

A toxicological study helps to determine two key factors influencing the development of the clinical picture: the nature of the toxic substance and its dose. Knowing this, it is easier to determine the tactics of management - for example, whether it is necessary to hospitalize the patient or is it enough to leave him under observation for a while. If the serum concentration of a toxic substance is known, the decision is more confident about the use of a specific antidote or about procedures that ensure the elimination of this substance (for example, initiating or stopping hemodialysis), transferring the patient from the ICU, or discharge from the hospital. Thanks to accurate information about the degree of exposure, a doctor from a poisoning center, who does not directly observe the patient, can nevertheless give advice. Finally, a positive test result for ethanol or drugs in a patient presenting with an injury also has predictive value, indicating an increased risk of injury in the future.

Toxicological data, acting as the "gold standard", may confirm the diagnosis of poisoning based on the clinical picture, or raise additional questions. Having received this data, the doctor more confidently assesses the situation (for example, whether the dose of the drug taken by the patient inadvertently is toxic or not). Such confidence allows not to waste time on an in-depth examination of the patient, if his condition is stable. This is especially important in a situation where the doctor deals with many patients at once and is forced to pay less attention to each of them.

Doubts about the correctness of the diagnosis should, if possible, be excluded if a toxicological study is necessary for forensic reasons. Thus, drug testing, while often performed for purely medical purposes, is almost always also forensic testing. Cases of intentional poisoning, accidental or intentional intake of toxic or narcotic substances by children, drug overdose in the elderly require careful documentation. If the results of the analysis can be used to confirm someone's criminal activity, it should be carried out in a forensic laboratory, following all relevant rules and procedures.

The results of the analysis obtained in the laboratory are recorded in the medical record and, in case of any problems, can serve as additional confirmation of the correctness of the diagnosis. But careful documentation of a toxicology study is important for more than just legal reasons. Because medical toxicology is a field that does not typically involve drug testing on human volunteers, documented clinical observations are the main source of new knowledge. Accurate data, for example, on the concentrations of toxic substances can be key in comparing and summarizing the results of such observations. Fixation in the medical record makes it easy to find them for retrospective studies. In addition, analyzes for scientific experimental studies can be carried out in the toxicology laboratory.

The most important thing for the optimal operation of the toxicology laboratory is good communication between its employees and the attending physician. The doctor should be aware of the capabilities of the laboratory: which toxic substances can be determined, which of them are measured quantitatively, and which are simply detected, how long the analysis takes. If you need a toxicological study, you need to know which substances are determined by the laboratory in the standard mode, which are on special request, and which cannot be detected, even if they are present in the sample in toxic concentrations.

In order to avoid erroneous results in a toxicological study, the correct preparation of the test sample is very important; however, the requirements of different laboratories may differ. As a rule, serum (red stoppered tube) or heparinized plasma (green stoppered tube) is needed for quantitation, but not citrated or EDTA plasma (blue or purple stoppered, respectively). EDTA and citrate bind divalent cations, which may be important as cofactors for enzymes used as reagents or labels in analysis. In addition, EDTA and citrate are used in the form of solutions, resulting in a dilution of the sample. Do not use disposable serum or plasma tubes: the substances contained in the sample may diffuse into the gel contained in the tubes, due to which the result of the analysis will be underestimated. For toxicological screening, a urine sample is generally preferred, as urinary concentrations of the substances of interest are usually higher. This makes it possible to compensate for the lower sensitivity that is characteristic of methods designed to detect a large number of substances. Usually 20 ml of urine is sufficient.

If a physician, when submitting a request to a laboratory for toxicological testing, suspects the presence of a particular toxic substance in a sample, it is important that he or she discloses this. This is often overlooked, while the laboratory may test for the suspected substance first and still use a more sensitive and specific technique. As a result, the analysis will be performed more quickly and accurately.

In unusual or confusing cases, laboratory personnel can help determine the best course of action for toxicology testing. The capabilities of the laboratory are often not limited to the declared list of tests carried out. Employees of most laboratories are interested in additional analyzes and provide advice free of charge.

Contact with the laboratory is also very important if the result of the toxicological analysis obtained does not correspond to the clinical picture; in the laboratory they are well aware of why this can happen. The most common cause of this is the presence of impurities in the sample or errors prior to testing (pre-analytical errors). The presence of foreign substances in the sample can both overestimate and underestimate the test result. An example is hemoglobin, which absorbs light in the wavelength range used in spectrophotometric analysis. Examples of preanalytical errors leading to incorrect and confusing toxicological test results are: poor labeling of the sample; ingestion of solutions for intravenous administration; incorrect sampling time; technical errors during sampling. If an error is discovered in the laboratory, it is all the more important to report it so that the laboratory staff can find the causes of the error and henceforth not repeat it.

Chemical-toxicological analysis - a specific analysis of objects of biological and non-biological origin for the presence of toxic substances (toxicants). The task of chemical-toxicological analysis is to establish the nature and concentration of various toxic substances (organic and inorganic, natural and industrial or artisanal, solid, gaseous and liquid) with stable properties or actively metabolized in the body and give a conclusion about their toxicity. The objects of chemical-toxicological analysis can be blood and urine, saliva and sweat secretions, cerebrospinal fluid, the contents of the gastrointestinal tract, liver, brain, spleen, kidneys, skin, hair, as well as muscle and tooth tissues, odors, etc.

The detection of substances of a heterogeneous in structure, an indistinctly defined range of compounds in various complex and unstable biological objects and the high accuracy of their identification during normal analytical work in a time-deficit mode are possible through a strategic concept, which consists primarily in the systematization of the analytical process.

Systematization involves the necessary compromises when choosing the optimal conditions for the analytical process (preparation of a sample for analysis, choice of methods, analysis itself, competent interpretation of the results).

The relative probability of detecting any substance in the test material does not depend on the toxicity of the compound and the statistical frequency of its use, it is considered only as a cause of poisoning.

In addition to systematization, adequate data are needed to streamline analytical signals, i.e. standard reference substances that can lead to real compounds and their perfect identification.

That is why the system of methods in chemical-toxicological analysis is wide-ranging, containing a large number of analytical methods. The methods used should have very low limits of detection and provide reliable analytical signals from a minimum amount of a substance.

Depending on the tasks set, there are three options for chemical-toxicological research.
Analysis of objects with known toxic substances, including a known dose of the accepted toxicant, is an analysis for a known, or so-called directed analysis, i.e.

e. under the established circumstances of the ingestion of a toxicant into the body (intravenous, oral, inhalation and other routes of entry).
If there is only indirect information about the circumstances of the poisoning, indicating its possible cause, the nature of the toxic substance can be predicted on the basis of the clinical picture of the poisoning or revealed as a result of a postmortem autopsy (in the event of the patient's death).
The third option is the most complicated, when there is no information at all about the nature and concentration of the toxic substance. In chemical-toxicological analysis, this type is called non-directional, i.e., analysis for the unknown. At the same time, the use of one, even the most informative method does not give grounds for the conclusion about the complete determination of the components of the mixture, since in principle it is not known whether the received signal corresponds to one or several individual compounds.

The analysis strategy is built depending on its features (directional or non-directional). If in the first case, reference information or other literature data can be used to select the optimal conditions for analysis, then in the third, most complex variant, a methodological technique called screening is used, i.e., stage-by-stage detection of group affiliation, and then individual detection and identification of toxic substances. In all cases of chemical-toxicological analysis, false positive and false negative results are obtained. The first of them are associated with the insufficient selectivity of the detection methods, and the second - with the insufficient sensitivity of the chosen methods of analysis.

False-negative response - a negative result for the test substance obtained in the analysis of an object containing this substance. The false negative response is inversely proportional to the sensitivity of the analytical method: the higher the sensitivity, the fewer false negative responses and more positive ones.

False-positive response - a positive result for the test substance obtained in the analysis of an object that does not contain this substance. A false positive response is the most serious error of an analytical chemist and is related to the specificity of the method used. For example, for immune methods it is possible to reduce the level of separation concentration (cut-off) to the sensitivity threshold of the method, which is usually several times lower than the cut-off. In this case, the number of false negatives will decrease and the number of false positives will increase. Ceteris paribus, one of the most important reliability parameters is the sensitivity of the research methods used (it is defined as the minimum concentration of a substance in an object that is discovered with high probability).

Another, even more significant parameter is the specificity of the methods used, determined by the ability of the method to distinguish one or another compound among many others.

The reliability of a positive or negative answer depends on numerous factors:
prescription and frequency of consumption of a toxic substance (contact with it);
how it enters the human body;
age, weight, dietary, dynamic, ethnic, individual variations in the absorption, metabolism and excretion of xenobiotics;
state of hepatic and renal functions;
pH and volume of urine;
sensitivity and specificity of the applied method of analysis;
proper organization of receipt, acceptance and storage of research objects (biomaterial, objects of non-biological origin);
thoughtful and clear documentation of the entire work process;
constant monitoring of the serviceability of equipment and the purity of all reagents;
highly professional staff.

Each stage of the chemical-toxicological analysis must be controlled by:
the use of a standard reference substance;
verification of correctness (calibration of performed operations);
reproducibility checks (statistical processing);
analysis conditions control;
modeling.

Systematic verification is necessary at the most vulnerable stages.
Sampling. Eliminate the possibility of destruction of physical evidence or falsification of the object, as well as due to the small mass of the sample, its contamination or changes in the chemical composition under the influence of the environment.
Sample preparation (stage of justified risk of partial or even complete loss of analytes). The operation must consist of strict and logically justified actions aimed at preserving the analyte. Recommend carrying out express test analyses. At this stage, only a limited number of methods allows analysis without prior preparation, i.e. directly in the biomaterial and other objects (immunological, chemical, etc.).

For most methods, the stages of sample preparation and concentration are obligatory. At present, there is no method by which, in one simple procedure, all encountered toxic substances at low concentrations can be quickly detected and accurately identified. That is why the process of detection and identification takes place in two methodological stages: screening (indicative) and confirming (identifying).

Screening tests
Methods of the first stage should have high performance and sensitivity level, sufficiently wide coverage of classes of toxic compounds, but not necessarily high specificity. At this stage, it is important to get a minimum of negative answers and a maximum of positive ones, however, with this methodological approach, there is a significant (10-15%) number of false positive results. The second step is to remove (ideally) false positives. His methods are often less productive but more highly specific. In the practice of chemical-toxicological analysis, the standard methods of the first stage are thin-layer chromatography and immunological research methods.

Thin-layer chromatography is available, cheap, covers a wide range of various classes of toxic substances, and is quite high-performance. The disadvantages of thin layer chromatography include laboriousness, work with harmful substances (solvents), and difficulties in interpreting the results. High-performance thin-layer chromatography is much more sensitive.

Confirmatory Tests
It is accepted in analytical toxicology that the initial detection of a toxic substance should be confirmed, if possible, by studies based on other physicochemical principles. In some circumstances it may be acceptable as a confirmatory test to use the same analytical system as in the primary study, such as in gas-liquid chromatography, if chemical derivatization (sylidation or acetylation) leading to a change in retention time is used. At the same time, confirmatory analysis with reuse of a gas-liquid chromatography system with a similar but not identical column is usually unsuitable, since the relative retention time data of many substances will not differ significantly.

The reuse of radioimmunoassay to confirm positive results obtained by another immunoassay (in particular polarization fluoroimmunoassay) cannot be accepted as acceptable. The test substances in the first method will have the same cross-reactions as in the second, since specific antibodies can react to the same toxic substances or substances similar to them.

Immunoassays have a high sensitivity, superior to that of thin layer chromatography (except for high performance thin layer chromatography), and higher specificity with respect to the class of substances for which they are made. They lend themselves to simple automation. Immune methods are clearly superior to TLC screening in detecting toxic substances consumed in milligram and submilligram amounts (eg, hallucinogens). In cases of acute poisoning, deaths, when the doses of a toxic substance are increased due to an overdose, TLC screening is a completely satisfactory method.

Disadvantages of immune methods:
manufactured kits (diagnosticums) are currently too expensive for screening search:
the range of diagnosticums is quite limited;
immune methods serve as a method for determining the group affiliation of substances;
the course of the immune response can be disrupted by simple falsification of the sample.

Gas chromatography with mass spectrometry is the second confirmation method, it combines high-performance capillary column chromatography separation and a highly sensitive molecular-identifying mass spectrometer.

Gas-liquid chromatography with a plasma ionization detector and high-performance liquid chromatography are the next most reliable confirmatory methods. These methods have a greater separating power than thin layer chromatography, making them more suitable for confirming results obtained by thin layer chromatography.

To use thin layer chromatography as a confirmatory method for immune tests or vice versa - there is no single point of view on this issue. On the one hand, it is considered an insufficiently reliable confirmatory method for solving legal problems, but reliable enough for solving clinical problems. With regard to the use of the immune method to confirm data by thin layer chromatography, it must be remembered that the immune methods confirm the presence of not any individual substance, but a whole class of substances, often having different toxicological significance. In addition, in the cannabinoid assay, immune methods can give 4 to 21% false positive results, which is unlikely to be reliable confirmation in this study. The combinations "immune methods-TLC" or "TLC-immune methods" require the use of another confirmatory method.

ELISA with varying cross-reactivity can sometimes be reused to justify primary screening. Confirmation of a result in a single extract of the same sample is not considered acceptable as this does not exclude the possibility of contamination of the extract during the extraction process. That's right - to confirm the identity of the detected substance in different extracts of the same sample. Determination of the quantitative content of the desired substance can be simultaneously a confirmatory method of identification if the substance being determined was initially detected by a method that differs significantly from the first.

To verify the identification of a particular toxic substance, it is recommended that, if possible, several samples of the sample be available. If only one sample is available, it should be mandatory to repeat the determination in different cases and using adequate control positive and negative tests on a similar matrix in samples of a similar type. The use of confirmatory identification methods is recommended for all types of toxic substances, including ethanol and carbon monoxide.

HTI - laboratory analysis of urine, the decoding of which is presented in the medical certificate in the form 454 / y - 06.

This document may be required by a person in various life situations, for example, when applying for a job in certain positions, as well as in the traffic police in order to prove that at the time of the accident the driver of the car did not have (presence) narcotic substances in the body.

HTI (HTI) - a laboratory analysis of urine with a detailed transcript. It is carried out in order to detect the presence of alcohol in the body and psychotropic substances. In some cases, this analysis is carried out in order to identify toxic substances with which the person was allegedly poisoned.

This research method has a number of advantages. Firstly, it is the ease of collecting biomaterial, and secondly, laboratory research is carried out quite easily and quickly. This analysis is simply necessary in some cases to establish legal justice.

Deciphering the analysis

Deciphering the results of this laboratory study, although it is a very important step, but also does not take much time. IN help with results any impurities should be noted if present in the person's urine. In addition, their number is also indicated.

If necessary, the doctor can determine how long before the analysis the person used alcohol or any drugs. Since this study is simple, the results are rarely erroneous.

Inaccuracies may occur due to the fault of a laboratory employee, due to equipment failure.

Prohibited products that the analysis reveals

If laboratory test results turned out to be positive, then in the transcript the doctor must indicate the name of the chemical that is present in the biomaterial. These include:

• cocaine metabolites;
• opiates;
• marijuana;
• amphetamine;
• methamphetamine.

The transcript indicates not only the fact of the presence of these illicit drugs, but also their number. In most cases, the time when a person consumed alcoholic beverages or took drugs is determined.

How long do drugs stay in urine?

Any chemical preparations are contained in the urine for several more days after their use. Thus, opiates contained in the urine are a sign of the use of one of the most difficult drugs - heroin. If this quality is removed from the blood within 2-3 hours after consumption, then it is contained in the urine for another two days.

Amphetamines and methamphetamines- Prohibited substances that affect the central nervous system. They are contained in the urine for the next 48 hours, from the moment of introduction into the body.

Cocaine, in most cases, is consumed by inhaling the substance through the respiratory tract or rubbing it on the gums. The substance is contained in the urine for 6-8 hours, but can persist up to a day.

Marijuana is a narcotic substance of plant origin. May be present in urine from 24 hours to several weeks.

Analysis readiness terms

HTI urinalysis is carried out both in public medical institutions and in private laboratories. The terms for which the analysis will be completely ready and deciphered, usually do not exceed 24 hours.

Sometimes, the analysis is carried out by an express method, using special test strips. This method is used more often in cases where analysis is needed by individuals, for example, parents want to test their child for drug use.

If the results are necessary to perform any legal action, for example, to confirm in the traffic police the fact that the driver was in a state of drug intoxication at the time of the accident, then this laboratory test is used.

How to cheat research?

If a person before the analysis still used narcotic substances, then he is interested in the question of how to bypass the laboratory study, or rather, to make the results incorrect. There are several ways to do this.

Substitution of biomaterial. This method implies that instead of his urine, a person will take the biomaterial of a "clean" donor to the laboratory. It is possible to make a substitution only in the case when a person takes the material for research to the laboratory on his own. For example, this analysis is necessary when applying for a security guard position. And hardly anyone will control the material intake in this case.

Narcotic substances are able to escape from the urine if you hold the liquid for several hours in the open air. As a result, the information indicated in the transcript of the analysis will be distorted.

You can agree with the laboratory staff on the substitution of the result. For this method, you must be familiar with the medical staff.

Another option - acceleration of metabolic processes in organism. Of course, this can only be done if the date of the laboratory test is known in advance. The essence of this method is to remove the remnants of drugs from the urine, by natural leaching. To do this, you need to drink plenty of fluids for 1 - 2 days before the analysis.

Taking detox medications that are aimed at removing toxins from the body. The disadvantage of this method is that the content of this medicine may be indicated in the decoding of the results.

It should be remembered that the substitution of the results of the analysis is a criminally punishable act.

Preparation for analysis

If a person has not used any illegal drugs, and wants the results of his HTI urinalysis turned out to be as accurate as possible, then he needs to know some rules.

They are to prepare for the laboratory test. Before visiting the laboratory, it is necessary to carry out hygiene of the genitals and anus. It is recommended to transfer the biomaterial in a clean container. It is better if it is a special container that can be purchased at any pharmacy. It is necessary to give urine in the morning.

Naturally, a few days before the analysis, it is necessary to completely eliminate the use of alcohol, drugs, and reduce the number of cigarettes smoked. If possible, it is necessary to refuse to take any medications.

traffic police control

Since recently, HTI - an analysis for narcotic substances is required to pass all motorists in order to to get right or driver's license. It is extremely difficult to deceive the result of the analysis in this case.

However, for drivers who abuse alcohol or drugs, there is an option to replace the biomaterial - buying artificial urine. This substance has already gained some popularity and is sold in specialized online stores. But, nevertheless, one should not risk either one's health or a driver's license and pass an HTI analysis without using prohibited substances.

With the help of toxicological research, the presence of drugs or alcohol in the body is determined. For this purpose, an HTI-analysis of urine is carried out. It is necessary when applying for a job, when investigating an accident. The study is carried out in situations where it is necessary to prove the absence / presence of alcohol and drugs in the body.

Drugs that affect the psyche are called psychoactive substances. This definition includes all drugs that, when taken once, cause a change in consciousness. The systematic use of these substances leads to dependence.

After entering the body, drugs enter the blood, the brain. The breakdown of psychoactive substances occurs in the liver. They are excreted by the kidneys after a few days or weeks. During this period, they are easy to detect in urine.

Primary traces are determined in the urine 6-8 hours after ingestion. The time of their complete withdrawal from the body depends on body weight, individual physiological characteristics, duration of drug use, dose.

As a material for study, not only liquid is taken, but also hair, sputum released during coughing, feces.

To determine the type and quantity of narcotic drugs, expensive reagents and sophisticated equipment are used. This explains the high cost of the analysis. Express test is more affordable. It detects 14 types of drugs in the studied liquid. The disadvantage of this method is the inability to determine the quantitative content of toxic substances.

Identification of psychoactive drugs and determination of their concentration is included in the program of diagnostic and treatment examination. Benefits of HTI analysis:

• simple collection of biological material;
• a single urine test (the volume of urine is sufficient for both the first and the second study);
• high accuracy and information content of the research result.

Rapid toxic-chemical analysis of biological fluid is carried out in special laboratories.

Many people ask the question, what is HTI. This term is called a urine test for drugs and alcohol. In some situations, the study reveals the toxins that caused the poisoning of the patient. Often it is this analysis that allows you to establish the truth.

The chemical-toxicological research method allows to determine the content of psychotropic substances in the human body. The method is popular, since the sampling of biological material is carried out simply, the result is achieved quickly.

When to donate urine to HTI

The need for a urine test for CTI appears when you need to present an official document confirming the absence of traces of drug and alcohol use in a person's body. It is carried out in laboratories responsible for the accuracy of the result. The medical institution must be licensed for such research. The analysis must be carried out on appropriate equipment. The result is recorded in the official certificate of KhTI of the established form, it is signed and stamped.

The need for a certificate that a person does not use drugs may arise:

• when applying for a job as a security guard with the right to carry weapons;
• for admission to universities and colleges;
• when preparing documents for traveling abroad;
• employees of decreed areas (pilots of military and civil aviation, railway workers, drivers, police officers, bodyguards, employees of departmental escorts);
• young people when undergoing a medical examination before being drafted into the army;
• citizens suspected of using drugs;
• road accident participants to confirm the absence/presence of alcohol, psychotropic substances in the body.

A laboratory test helps to prove the guilt or innocence of a person.

There are freely available test strips, panels for urine and saliva analysis for drug and alcohol content. They allow you to determine at home whether a person is taking prohibited substances. This is important if there is a suspicion that one of the family members is taking drugs, because the earlier the problem is detected, the easier it is to get rid of it.

To obtain a referral for analysis in the laboratory, you must contact a narcologist.

What substances determines HTI

HTI-analysis of urine reveals prohibited substances:

• alcohol;
• amphetamines;
• cocaine;
• opiates;
• barbiturates.

With the help of a preliminary chemical-toxicological study, the presence of traces of substances is checked, their appearance is revealed.

Confirmatory analysis is carried out for 4 days. The study is carried out using chromatography (liquid and gas-liquid), spectrography. Screening shows the amount of psychotropic drugs in the studied material.

Rules for the collection and storage of samples

A urine test for drugs requires at least 50 ml of body fluid. The sampling should be carried out in a clean container. Pharmacies sell special plastic containers for tests. The algorithm of actions when passing urine for analysis:

• buy a plastic container;
• collect 100-150 ml of urine;
• close the container tightly with a lid;
• deliver the biomaterial to the laboratory.

Urine collection for research should be carried out correctly. For an accurate analysis, you should collect the average portion of the liquid. The initial portion contains too many substances, the final portion contains too little. The average allows you to determine the exact concentration of psychoactive drugs.

If the laboratory failed to send samples for detailed analysis in time, they are placed in a refrigerator. Short-term storage is carried out at a temperature of +5°C. The period of keeping biological material in the refrigerator should not exceed 36 hours.

For long-term preservation, the material is placed in a freezer. In the frozen state, the liquid can be stored for 72 days. It contains the remains of toxic substances necessary for further research. When urine is frozen, the markers of narcotic drugs contained in it do not lose their primary properties. They are easily found after defrosting.

After delivery of the biomaterial to the toxicological laboratory, it is thawed and further necessary manipulations are carried out.

Storage of urine samples should exclude the possibility of replacing the material with another person.

Features of the procedure

The study is based on the ability of urine to retain traces of toxic substances for 6 days after they enter the body. At the first study, the result of CTI becomes known 30 minutes after the analysis is taken.

The principle of analysis is that the studied liquid passes through absorbent filters. If prohibited substances are present in the sample, a reaction occurs between the immune antibody and the antigen present on the strip. As a result of the interaction, an antigen-antibody combination is formed.

The test strip is marked with divisions from 1 to 5. If there are no toxins in the sample or the concentration has not reached the threshold limit, 2 pink marks appear.

In the presence of narcotic drugs, a pink stripe appears.

In a conventional medical laboratory, it is impossible to conduct a study for the presence of toxic drugs. Accurate analyzes are carried out in special chemical-toxicological laboratories.

The procedure for a detailed analysis of urine takes place in 2 stages.

The HTI preliminary test detects the presence of psychotropic substances in the human body. The express method shows the absence / presence of toxic substances, determines the type of drug. One strip on the tester indicates the presence of psychotropic substances in the test material. The brighter the color, the greater the concentration of substances in the body. Two strips appear if no harmful components are found in the urine. In addition to drugs, the HTI urine test is used to detect alcohol use.

If there is a need to clarify the number of prohibited substances, a re-analysis is carried out.

A quantitative study shows the concentration in the urine of narcotic substances. It is carried out on complex equipment in several stages. This analysis is important for determining the concentration of narcotic substances. The accuracy of the obtained data depends on the storage conditions of the biological material and the time of urine collection.

The decoding of HTI is recorded in a special certificate.

The duration of drug retention in urine

The less time passes after the use of psychoactive substances, the clearer the result of the analysis will be. The period during which traces of drugs are determined in the biological fluid is affected by:

• body mass;
• dosage;
• type of substance;
• frequency of use.

With a single admission, the detection period is:

• 2 days - amphetamines and methamphetamines;
• 3 days - morphine and heroin;
• 4 days - cannabinoid derivatives (for example, marijuana);
• 5 days - cocaine.

With systemic use, the time to detect traces of drugs in the urine ranges from 48 hours to 72 days.

Identification of traces of psychoactive substances in urine helps to start therapy on time. The success of the treatment depends on the stage at which the problem is identified. HTI is recognized as the most accessible way to detect traces of illegal drugs in the body. In some situations, the study allows you to prove the innocence of a person.

A urine chemical-toxicological study (CTI) allows you to check whether a person has taken alcohol, narcotic substances or neurotropic drugs. This type of research has a number of advantages over the blood drug test. The biomaterial is easy to collect, high activity of psychotropic substances remains in the urine, so they are easy to determine. The drug test of biological fluids is carried out by specialized toxicological laboratories. In a conventional clinic, such an analysis is not available.

The essence of the study

The chemical-toxicological analysis of urine is evidence or refutation of a recent intake of narcotic substances by a person. They are metabolized in the liver, excreted by the kidneys within a few days or even weeks. During this period, metabolites are easily detected in the urine. The first traces of drugs in the body fluid can be determined only 6-8 hours after consumption. Chemical-toxicological analysis is a rather complicated procedure. Chromatography or chromato-mass spectrometry is used to determine the group of a narcotic substance and calculate the concentration. Due to the need to use expensive reagents and equipment for CTI, the cost of analysis in the clinic is high.

To determine narcotic substances, you can also conduct a more affordable rapid test, which uses the technique of thin layer immunochromatography. It has high sensitivity, allows you to detect up to 14 types of drugs in the sample using test strips. The disadvantage of the method is that it is impossible to determine the density of the substance in the body and the degree of drug intoxication. HTI is not a standard analysis; it is required to pass it only in special cases.

When should I take urine for HTI?

A urine test for drugs is mandatory for people of certain professions - policemen, drivers, security guards, pilots and air traffic controllers, etc. The test is also assigned to the perpetrators of traffic accidents. There are other reasons to pass urine for chemical-toxicological analysis:

• diagnosis of drug addiction;
• control of drug addicts during rehabilitation;
• the need for a medical examination during the trial;
• obtaining a driver's license, a gun license;
• registration of permission to travel abroad, residence permit, etc.

A positive result from a single urine test is not enough to determine drug addiction. It is necessary to be examined by a narcologist, to pass repeated tests, only after that it is possible to make a diagnosis and prescribe rehabilitation in a drug dispensary. The choice of HTI methodology depends on the purpose of the analysis, for example, rapid tests are not used for forensic examination.

Analysis algorithm

Chemical-toxicological examination of urine is carried out in several steps. At the first stage, a qualitative analysis is made, the presence and type of a narcotic substance in the urine is determined. If the test result is positive, the material is stored for further research. At the second stage, a quantitative assessment of the content of certain substances is made by chromatography. The study can last 4-5 days. This step is especially important when testing for drug addiction in the urine. Only knowing the quantitative indicators, one can judge the degree of drug intoxication. The accuracy of the results depends on the time of collection of the material and the conditions of its storage.

Rules for the collection and storage of samples

Special preparation for the analysis is not required, the basic principle of an accurate study is that the sooner a sample is taken, the more reliable the result will be. Rules for submitting biomaterial for toxicological examination:

• purchase a plastic container at the pharmacy;
• urinate into a container (100–150 ml is enough for analysis);
• tightly screw the container with a lid;
• within a day to deliver the material to the laboratory.

Urine can be stored in the refrigerator at a temperature of 2-8°C, but not more than 36 hours. The collection of material must be supervised by a responsible person to avoid substitution. If it is not possible to send a sample for screening in the first few days after collection, it should be stored at a temperature of about 0 ° C. Alcohol and psychoactive substances under such conditions do not oxidize or decompose.

What substances determine HTI?

Modern methods make it possible to determine the following types of drugs in urine:

• Cannabinoids (active components of hashish and marijuana) - cannabinol, tetrahydrocannabinolic acid (THC). A synthetic analogue of THC is part of the banned smoking blend Spice.
• Cocaine is a hard drug.
• Opiates - morphine, codeine, heroin. Morphine and codeine were isolated from the opium poppy and are still used today as painkillers. Heroin is a synthetic derivative of morphine and is classified as a hard drug.
• Opioids - methadone. Drugs with methadone belong to the category of soft drugs, they are used in substitution therapy for heroin addiction.
• Amphetamines - methamphetamine, ecstasy (methylenedioxymethamphetamine - MDMA).
• Barbiturates - phenobarbital. The substance belongs to psychotropic, is part of many sedative, analgesic drugs.
• Benzodiazepines.
• Ethylglucuronide is a metabolite of alcohol.

Urinalysis for some drugs may show a false positive result. For example, if a person regularly takes legal drugs with codeine, there will almost always be traces of morphine in their urine samples, and the same goes for barbiturates. Separately, it should be noted the popularity of the synthesis of various "designer drugs", such as, for example, pyrrolidinovalerophenone. Detection of their use is difficult, so the study may show a false negative result. Although some degradation products can be detected in biological fluids using chromatography.

How long do drugs stay in urine?

Groups of narcotic substances differ in chemical nature, are converted differently in the body, and therefore the timing of their complete excretion in the urine is also different. If one drug can be seen in the sample even 10 days after consumption, then there are no traces of the other on the third day. The period of transformation and excretion of the drug by the body depends on the dose taken, the weight of the person, the work of his liver and kidneys. Cannabinoids, for example, tend to accumulate in adipose tissue, so they are excreted from the body for a long time. Heroin and codeine are immediately converted to morphine, which can be found in the biomaterial. The shelf life of psychoactive substances and their metabolites in the urine: