In former times, epidemics of such a serious infectious disease as typhoid fever led to the death of thousands of human lives. Thanks to strict sanitary and epidemiological control, outbreaks of this dangerous intestinal infection have not been observed in our country for a long time. However, in African, Asian and South American countries with hot climates, the incidence of typhoid fever is still very high. The ideal habitat for the causative agent of this disease (typhoidal salmonella from the Enterobacteriaceae family) is contaminated water bodies, poorly treated drinking water, improperly stored dairy and meat products, where at high air temperatures harmful microorganisms begin to actively multiply. The bacterium is excreted in the feces of the bacteria carrier and enters the mouth of a healthy person through dirty hands, food, or common objects (fecal-oral route of infection). To identify this infectious pathogen, laboratory tests of urine, feces, bile are carried out, and a blood test for typhoid fever is also prescribed.

Indications for testing

First of all, typhoid salmonella affects the intestines, then the regional (nearby) lymph nodes, after which it penetrates the circulatory system and causes general intoxication of the body. Indications for donating blood to detect this bacterium are high body temperature, headache, depression, weakness, dry tongue, pain in the right hypochondrium, red rashes on the abdomen (roseola), clouding of consciousness. Laboratory blood tests when diagnosing this pathology are carried out without fail, since similar symptoms are also characteristic of pneumonia, malaria, etc.

Hemogram

This term hides a general clinical blood test, which is an integral part of the diagnostic procedures for any infectious diseases. The presence of typhoid fever may be indicated by the following indicators: the level of leukocytes in the blood is greatly reduced (leukopenia), there are no eosinophils, and the erythrocyte sedimentation rate (ESR) is increased.

Bacteriological research

Next comes the direct detection of the typhoid pathogen (blood culture). For this purpose, venous blood is taken, inoculated on a special nutrient medium and placed in a thermostatic apparatus in which a high temperature is created. Under the influence of heat, entire colonies of bacteria are formed, suitable for microscopic examination. Blood culture is considered the most accurate early diagnostic method for detecting typhoid fever.

Immunological study

Since the immune system must respond to the introduction of a foreign agent, around the end of the first week of the disease, antigens and antibodies to the infectious pathogen begin to form in the blood. For immunological research, blood serum is separated, in which the titer (level) of antibodies is determined. This analysis is called the passive hemagglutination reaction (RPHA). In a sick person, the antibody titer can be 1:40, and in a recovering person it can reach 1:2000, so this blood serum test is carried out every 5 days.

Preparing for the test

In order for the results of general clinical, bacteriological and immunological tests for typhoid fever to be reliable, it is necessary to prepare accordingly for the blood test. If possible, it is advisable to stop taking any medications three days before the procedure. Two days before laboratory tests, alcoholic beverages are prohibited. On the day of visiting the blood donation point, you will have to stop eating dairy products, eggs, butter, fried, smoked and spicy foods. An hour before the tests, you need to refrain from the bad habit of smoking. All these factors can cause biochemical, metabolic and hormonal changes in the body that can change laboratory parameters.

A blood test for typhoid fever is a necessary procedure for making a correct diagnosis, but it is better to prevent the development of this dangerous disease. It is necessary to keep your hands clean, thoroughly wash fruits and vegetables, avoid eating street food, and fight flies - active carriers of this infection. It is especially important for workers in the food industry, preschools and medical institutions to strictly observe sanitary and hygienic rules.

Typhoid fever is an acute infectious disease characterized by prolonged fever, toxicosis, enlarged spleen and liver, enteritis, and skin rash. A blood test for typhoid fever is carried out to distinguish the disease from tuberculosis, brucellosis, typhus, and other diseases characterized by intoxication and fever.

Indications

The causative agent of typhoid fever is transmitted through household contact, most often through contaminated water. Without treatment, the disease is life-threatening due to the development of complications such as intestinal perforation.

Of the laboratory tests for diagnosing the abdominal type, the most valuable is the isolation of the pathogen from the patient’s blood. Additionally, hematological studies are carried out and the number of leukocytes and the ratio of their formed elements are determined.

Preparation and delivery of analysis

To achieve the right results, you must stop taking medications three days before the procedure. Two days before the typhus test, you should not drink alcohol. On the day of donating blood for typhoid fever analysis, you must avoid foods such as eggs, dairy products, smoked foods, spicy seasonings and fried foods. Do not smoke an hour before donating blood.

For diagnostic purposes, a blood test for typhoid fever is performed according to the following indicators:

• Hemogram, or. Carried out when infectious diseases are suspected. The detection of typhoid fever can be indicated indirectly by leukopenia, absence of eosinophils and;
• Bacterial culture. It may take up to five days for microflora growth to appear and to be identified;
• is able to detect the presence of proteins indicating the acute course of the disease;
• for typhus, which makes it possible to detect antibodies on the fourth day of illness;
• for typhus;
• RNHA is a reaction of mediated (indirect) hemagglutination.

Positive results confirm the presence of antibodies to the pathogen. This indicates either the presence of the disease in the acute phase, or a past infection.

If the test result for typhoid is negative, this indicates either that the disease has just begun, or that it has been suffered for a long time, or that the person is healthy and has never had typhoid fever.

Sometimes tests give a false positive result. The cause may be other Salmonella infections, hemolysis of the blood sample, or antibiotic use.

Differential diagnosis of typhoid fever can be complicated. The independent laboratory Invitro came to the aid of public medical institutions. The Invitro laboratory network uses the latest test systems from the leaders of the global pharmaceutical industry in Ukraine, Belarus, Kazakhstan and Russia.

Invitro successfully diagnoses a variety of diseases, including typhoid fever. The basis for confirming the diagnosis is the isolation of Salmonella typhi from the patient's blood.

The pathogen is detected in the blood by bacteriological (blood culture on nutrient media) and serological methods (RPHA rapid test for antibodies). Rapid tests are inferior to bacteriological methods in specificity, since they detect antibodies to other microbes of the genus Salmonella. In addition, the test also reacts positively to antibodies indicating a previous illness. Therefore, a repeat test is indicated after five days. If the antibody titer increases, then the disease is in the acute phase.

No special preparation is required for taking blood for analysis in Invitro. Blood must be taken on an empty stomach, or four hours after breakfast or lunch.

Typhoid fever is information for the doctor, who makes the final diagnosis.

Treatment and prevention

Patient care is of great importance in the treatment of typhoid fever. Patients are hospitalized, and during the critical stage of typhoid fever they are prescribed bed rest, which is extended after the temperature drops for another week. Then, the recovering person will be allowed to sit down, and after another week get up.

During hospitalization, the patient should drink as much as possible, preferably sweet tea. Food should be semi-liquid and high in calories

Treatment of typhoid fever is carried out in two directions:

• combating the pathogen and measures against intoxication and dehydration. The fight against the causative agent of typhus comes down to the use of antimicrobial agents. Measures against dehydration and intoxication are carried out using parenteral administration of appropriate drugs.

Depending on the situation, symptomatic drugs are used, cardiac, restorative and others. Patients with typhus are discharged from the hospital no earlier than three weeks after the temperature drops, subject to negative results of bacteriological tests.

Treatment and prevention of typhoid fever involves vaccination to prevent the recovering person from becoming a carrier of the bacilli. Prevention of typhus, excluding vaccination, consists of observing sanitary hygiene standards, monitoring the sanitary condition of food industry enterprises, catering and trade.

Personal prevention is washing hands, vegetables and fruits before eating and heat treatment of raw animal products.

Typhoid fever is a dangerous infectious disease caused by Salmonella S.typhi. You can catch typhoid fever through food, contaminated water, failure to follow simple hygiene rules (through unwashed hands), as well as from a carrier of the infection.

The initial signs of typhoid fever are in many ways very similar to various other infectious diseases, so if you suspect the presence of this infection in the body, it is necessary to do a test for typhoid fever for an accurate diagnosis. Only in this way can the fact of infection be confirmed and effective treatment be prescribed in a timely manner.

Indications for prescribing a blood test for typhoid fever

A test for typhoid fever is required if the following symptoms occur:

• Attacks of nausea, vomiting, abdominal pain.
• Signs of body intoxication: insomnia, loss of appetite.
• Unstable stool: constipation or vice versa diarrhea.
• Feeling of general malaise and weakness.
• Symptoms of dehydration: dry skin, thirst, coated tongue.
• A gradual increase in body temperature turning into fever.

The presence of typhoid fever is determined based on laboratory test results, medical history (patient survey), which may indicate characteristic signs of the disease and contact with a carrier of the infection. To prevent the occurrence of typhoid fever and comply with standard sanitary standards, blood tests for typhus are taken by working personnel of medical institutions, preschool institutions, as well as workers in the food industry, enterprises selling various food products, etc. at intervals of once a year.

What tests are prescribed to diagnose typhoid fever?

If there are signs of illness, a blood test for typhus should be taken before taking antibiotics. This condition is explained by the fact that after 2-4 days from the start of treatment, a blood test may give a negative result. In general, a number of the following tests are usually prescribed for such a study:

• Serological blood test(Vidal reaction). With its help, you can detect antibodies to the causative agent of typhoid fever on the 4-5th day of illness.
• General blood test. Such an examination is usually prescribed in the first days of the disease, but it only indirectly indicates the presence of typhoid fever.
• Biochemical blood test- detects acute phase proteins.
• Bacterial culture- the results of such a blood test can be obtained only after 4–5 days.

To detect antibodies to typhus, radioimmunoassay and enzyme immunoassay blood tests are used. The most common method of analysis, which is used to detect carriers of infection among employees in the food industry and to assess the effectiveness of vaccination against typhoid fever, is the research method using IRHA (indirect hemagglutination reaction). The material for this analysis is venous blood. To obtain the most accurate data, smoking is prohibited 30 minutes before taking the RNGA analysis.

If the blood test for typhus is positive, we can talk about an acute course of the disease, or about a previous infection. In addition, a positive result may indicate that the person is a carrier of the causative agent of typhoid fever. If the test results are negative, the doctor can conclude that a long time has passed after recovery, an early form of the disease (in the presence of appropriate clinical manifestations), or even the absence of infection in the body. A false-positive test for typhus is possible in the presence of cross-reactions with other pathogens of infectious diseases such as Salmonella.

How to properly prepare for testing for typhoid fever?

The main factors that influence the result of a blood test for typhus include:

• Eating. On the day of testing for typhoid fever, it is not recommended to eat fried, spicy, smoked and fatty foods, as well as butter, dairy products and eggs. With such an unhealthy diet, it is possible to have both a direct effect on the composition of the blood due to the absorption of food components, and an indirect effect - the effect of sample turbidity, shifts in hormone levels.
• Alcohol. Two days before donating blood for analysis, it is prohibited to drink alcohol, since it has an acute and chronic effect on many metabolic processes.
• Smoking. An hour before your visit to the blood donation point for analysis, you must refrain from smoking. The fact is that this bad habit changes the secretion of biologically active substances, which negatively affects the results of the study.
• Emotional and physical overload- cause biochemical and hormonal changes.
• Instrumental examinations, physiotherapy - may cause temporary changes in laboratory parameters.

In addition, when taking blood, the time of day is very important: each person has certain daily rhythms of activity and, in accordance with this, daily fluctuations in many biochemical and hormonal parameters, expressed to a lesser or greater extent for different indicators. If possible, it is advisable to donate blood for analysis on an empty stomach (at least 8 hours and no more than 14 hours of fasting, you can drink water as usual), avoid food overload the day before. The most optimal time to take blood tests for typhoid fever is in the morning, between 8 and 11 am.

4.50 out of 5 (5 Votes)

A diagnostic serological test for detecting antibodies to Vi-antigens of the typhoid pathogen in blood serum is intended to confirm or deny the fact of carriage.

Completion deadlines	7-8 days
Synonyms (rus)	Serological analysis for Vi-antibodies of the causative agent of typhoid fever in blood serum
Synonyms (eng)	Indirect hemagglutination assay for Salmonella typhi Vi antibodies
Method of analysis	Indirect hemagglutination reaction (IRHA)
Preparing for the study	The analysis is carried out in the morning, on an empty stomach. At least 8 hours must pass since the last meal.
	Avoid drinking alcohol at least 24 hours before taking biomaterial.
	It is not recommended to donate blood for serology after fluorography, x-rays, or physiotherapeutic procedures.
Biomaterial and methods of taking it	Venous blood

General information about typhoid fever and its detection

Typhoid fever refers to acute infectious intestinal diseases. It is characterized by a cyclic course with systemic damage to the intestinal organs, central nervous system, liver, and lymphatic system; general intoxication of the body, persistent bacteremia, in which the presence of bacteria is detected in the blood. The source of infection is sick, recovered bacteria carriers.

The causative agent of typhoid fever - salmonella Salmonella typhi, refers to intestinal bacteria.

The antigenic system of the pathogen is represented by antigens O, H, Vi.

Vi antigen is a virulence antigen, forming the resistance of the typhoid Salmonella pathogen to the body’s protective reactions. The presence of antibodies to Vi-antigens of Salmonella typhi during serological testing of blood samples serves as a marker of bacterial carriage.

Blood test method with Vi-antigen

Antibodies to erythrocyte Vi-antigens are detected using serological reaction of indirect hemagglutination, RNGA , using special diagnostics.

RNGA method:

• based on the ability of interaction between blood serum antibodies and antigens that are fixed on red blood cells (erythrocyte diagnosticum); the result of the reaction is aggregation of erythrocytes followed by sedimentation, agglutination;
• by the nature of the erythrocyte sediment, one judges the presence of antibodies (a characteristic “umbrella”) or their absence (a sediment in the form of a “dot”);
• is semi-quantitative; to carry out the reaction, dilutions of blood serum are used to determine the diagnostic titer;
• the minimum diagnostic titer during the reaction is 1:40;
• an increase in the diagnostic value of the reaction is observed when using repeated analysis (paired serum method);
• the reaction is highly sensitive and specific and can be used on the fifth to seventh days of the disease.

The main purpose of the study is to identify the carriage of typhoid Salmonella bacteria.

Analysis results and their interpretation

Test results may be positive or negative.

Positive answer:

• detection of antibodies to Vi-antigens of the typhoid pathogen in the blood (minimum diagnostic titer value 1:40) is considered as an indication of the fact of bacterial carriage and the need for repeated testing;
• the response records the titer value;
• may indicate an acute infection, a previous illness, or vaccination;
• in rare cases it may be false positive due to cross-reaction.

Negative answer issued if antibodies are not detected. A similar situation is possible both in the absence of infection with a typhoid pathogen and in the early stages of the disease.

Conducting this study is of particular importance to prevent the spread of typhoid fever by bacteria carriers.

Typhoid fever is a serious disease caused by infection. If left untreated, it can cause death in the patient. The causative agent is a bacterium belonging to the Salmonella species. Also known as "E. coli". This is a fairly tenacious microorganism that poses a threat to humans. If characteristic symptoms occur, the specialist will prescribe an analysis to determine the presence of the pathogen. Blood testing for typhoid fever is a simple procedure that helps determine the risk of developing the disease.

Microorganisms that cause disease enter the body through household means. Infection often clears up by drinking water. Without treatment, the disease is life-threatening as it provokes the development of serious complications. Among them are bleeding in the intestine and perforation of the intestine.

Among the studies carried out to diagnose typhoid fever, a blood test is considered more informative. As additional procedures, a hematological study is prescribed to determine the rate of red blood cell sedimentation, as well as the number of leukocytes. The ratio of their elements is established.

The procedure for collecting material and its research is carried out for individual organizations and their workers. Data on the results are entered into the sanitary book. To obtain a health certificate, employees are required to take a test:

1. Catering and food industry enterprises.
2. School and preschool institutions.
3. Public service organizations. These are workers of swimming pools, hotels, hairdressers, spas, baths.

This also applies to medical staff, pharmacists and drivers who transport food.

Preparation and delivery

In order for the results of the blood test to be correct, you should stop taking medications three days before the sampling procedure. You must not drink alcoholic beverages for two days. On the day of the procedure for collecting material to identify the causative agents of typhus, you must stop consuming milk and other products that contain it, smoked, spicy seasonings, and fried. Smoking is prohibited one hour before the blood sampling procedure.

Along with a blood test for typhoid fever, the following studies are also prescribed:

1. General analysis. Prescribed for suspected development of infectious pathologies. But typhoid fever can be detected indirectly. Leukopenia, eosinophil deficiency and an increase in ESR levels are also detected.
2. Bac sowing. The duration of the analysis is about five days. The material for research is taken from the mucous membrane of the urethra or vagina using a special swab. After which it is placed in a special environment and sent to the laboratory.
3. Biochemical analysis. Helps to record the presence of proteins that indicate the acute course of the pathology.
4. Serological blood test for typhus. The diagnostic method helps to detect antibodies already on the fourth day from the onset of infection.
5. Enzyme immunoassay to determine the presence of antibodies to typhus.

The duration of the blood sampling procedure is no more than 5-7 minutes. Many patients are interested in where the blood is taken from. The material is taken from a vein. To do this, the specialist treats the puncture site with a cotton swab dipped in an alcohol solution.

Then a tourniquet is applied above the elbow and a needle is inserted into the vein. Blood is drawn, and the puncture site is then treated again with a cotton swab soaked in alcohol. The patient should bend his arm at the elbow and wait 10 minutes.

How long does the analysis take?

The duration of a laboratory test to determine the presence of antibodies to typhoid fever ranges from 3 to 10 days. This depends on the method of studying biological material and the workload of the laboratory.

The attending physician will tell you how long the test is done and when to get it. Most often, the results of the study are ready within 4-5 days.

Decoding

A positive result is established in the presence of antibodies to microorganisms that provoke the development of the disease. These indicators indicate either the presence of a pathology that occurs in the acute stage, or an illness that has already been suffered.

In cases where the final result of a blood test for typhoid fever is negative, this indicates that the disease is just beginning to develop or that it was suffered some time ago. A negative result also means that the person is completely healthy and has not been infected with typhoid fever.

In some cases, a false positive result is noted. This may be caused by other infections such as Salmonella, hemolysis of the plasma sample, or prolonged use of antibacterial drugs.

Prevention

The most effective prevention is vaccination against typhoid fever. Vaccination is prescribed for children aged two years. Secondary vaccination – after three years. Vaccinations for adults are given in the event of a threatening situation, when there is a high probability of developing pathology, or when traveling to an area where a high level of disease has been established.

Immunity after vaccination, depending on the type of vaccine, lasts for 10 years. When traveling or working in unfavorable conditions, city areas, as well as their residents, it is recommended to revaccinate after 1-3 years.

Nonspecific measures to prevent the occurrence of typhoid fever include:

1. Hand hygiene. You should wash your hands after returning from the street, interacting with animals, and before eating.
2. Drinking boiled water. Avoid drinking water from unreliable sources.
3. Sterilization of dairy products. Milk should be boiled before use.
4. Carry out heat treatment of meat products.
5. Control the freshness of food.

For the purpose of preventive measures, timely detection of infection is carried out in people whose professional duties are related to the production or preparation of food. It is very important to monitor the health of children attending preschool institutions. Water supply and wastewater disinfection are also monitored.