Thymol turbidity test – sedimentary test, thanks to which qualitative and semi-quantitative changes in plasma proteins are evaluated. Thymol turbidity test is prescribed in combination with transaminases, alkaline phosphotase, and a sulemic test. The Maclagan test allows, first of all, to evaluate the protein-forming function of the liver. It is used for the diagnosis of liver lesions, systemic connective tissue diseases, kidney diseases. Blood serum is used for the study. The method of setting the thymol sample is photocolorimetric. Normally, the value of the thymol sample is 0-5 units.M.
Proteins in the blood in a certain ratio are represented by low-molecular protein albumin and globulins: alpha-1 and alpha-2-globulins, beta-globulin, gamma-globulin. Albumin, alpha-1-globulin, alpha-2-globulin and partially beta-globulin are synthesized in the liver. Beta-globulin and gamma-globulin are mainly formed in the spleen, bone marrow and lymph nodes. Proteins control the acid-base state of the body, determine oncotic blood pressure, and participate in the formation of an immune response. Special transport proteins carry cholesterol, bilirubin, iron, hormones, and medicinal substances.
When the liver is damaged, its synthetic function suffers, which causes changes in the ratio of blood protein components. The state of dysproteinemia develops. The protein molecules themselves are also transformed. Their characteristics may change – configuration, molecular weight, electric charge. These changes lead to the loss of colloidal stability of proteins. Violation of this important property of proteins is manifested in the fact that in pathological conditions they begin to stick together and precipitate. This is the main principle of the thymol test.
Currently, a thymol test is rarely prescribed. It was replaced by more specific biochemical studies. However, in some areas of medicine, the appointment of a thymoloveronal test has not lost its relevance. Infectious disease specialists prescribe a Maclagan test to diagnose viral hepatitis and determine the stage of the disease. In hepatology and toxicology, a thymol test is performed to assess the degree of damage to hepatocytes and as an indicator of the effectiveness of treatment aimed at restoring liver cells.
Indications and contraindications
Thymol turbidity test is prescribed for sudden febrile temperature, catarrhal phenomena (sore throat, coughing), symptoms of intoxication (headache, aching muscles and joints) and dyspeptic disorders (nausea, vomiting, bitterness in the mouth, heaviness in the epigastric region). These symptoms may indicate the initial manifestations of acute viral hepatitis A. The study is indicated for prolonged joint pain, fever, skin changes. Such signs may be manifestations of systemic lupus erythematosus, systemic scleroderma, dermatomyositis.
Thymol turbidity test is one of the liver tests and can be prescribed in combination with other biochemical parameters – bilirubin, alkaline phosphotase, prothrombin index, transaminases. With a cumulative assessment of the results of the study, it is possible to recreate a complete and real picture of the degree of liver damage.
Thymol turbidity test is used for differential diagnosis of jaundice. With parenchymal (hepatic) jaundice, the thymol test is positive. In case of mechanical jaundice associated with obstruction of the biliary tract, in 75% of cases it is negative. The study can be prescribed in the absence of symptoms in cases when the patient indicated long-standing and unknown liver diseases during the collection of anamnesis, or if characteristic diffuse changes were found during liver ultrasound. The analysis is performed to track the dynamics and control the effectiveness of therapy for acute viral hepatitis, malaria, toxic hepatitis, autoimmune diseases. There are no contraindications to the thymol test.
Preparation and blood collection
Blood for the thymol turbidity test must be taken strictly on an empty stomach in the morning. Dinner should be no later than 8 hours before blood sampling (optimally – at least 12 hours of pre-starvation). It is forbidden to drink juices, carbonated water, coffee and tea. You can drink pure water without sugar.
In the treatment room, in conditions of sterility, a medical worker punctures the vein of the ulnar fossa or hand. Several milliliters of blood are collected into a regular test tube without an anticoagulant or a vacutainer. The container with blood is marked, indicating the patient’s full name, time and place of blood collection, placed in a special container and handed over to the courier.
In the biochemical laboratory, 0.1 ml of blood serum is used to conduct a liver test, which is added to 6 ml of veronal-medinal buffer with an acidity of 7.8. Then a saturated thymol solution is added to the resulting mixture, and the test tube is placed in a tripod for 30 minutes to settle. If after half an hour the solution has become intensely cloudy, it means that the protein particles have combined and formed large globulin-thymolipid aggregates. Next, the degree of turbidity of the solution is measured using a photocolorimetric method, using a special calibration graph. It is believed that the thymol test is positive if the amount of albumins in the blood serum decreases, the content of beta-, gamma-globulins and beta-lipoproteins increases.
The Maclagan test is carried out by a medical laboratory technician for one hour. If there is no urgency in obtaining the analysis result, then the response is issued in the evening or the next day.
The thymol sample is measured in Maclagan units (units m.). The result is considered negative if the degree of turbidity is less than 4 units. The maximum concentration is 4-5 units.M. When deciphering the data obtained, it should be taken into account that the results of the analysis may be affected by the consumption of very fatty foods before blood donation. A slight increase in the results of the test (by 1-2 units) is possible with prolonged use of hepatotoxic drugs, for example, antimycotic drugs or hormonal contraceptives based on estrogens.
Thymol turbidity test is considered positive if the result exceeds 5 units.M. In the initial stage of acute viral hepatitis A (Botkin’s disease), elevated indicators of the thymol test can be called a marker of this disease. The Maclagan test is the very first of the biochemical parameters to react to the virus replication that has begun in liver cells. Only then do transaminases, bilirubin begin to rise and other liver tests change.
Increased results of the thymol test are determined in infectious and toxic hepatitis, cirrhosis and liver tumors. Positive testing indicates a decrease in the synthesis of albumins by the liver and the formation of an immune response by increased formation of beta- and gamma-globulins in the reticular-endothelial system. As a rule, in those who have had viral hepatitis, a thymol test gives a positive result within 6-12 months after discharge from the hospital.
A positive reaction of a thymol test is not a strictly specific indicator for liver diseases. An increased value of the thymol test is detected in nephrotic syndrome due to kidney diseases. The reason is a decrease in albumins in the blood due to proteinuria, hyperlipidemia and increased synthesis of the globulin fraction.
A positive thymol turbidity test is noted for systemic connective tissue lesions, malignant neoplasms, pancreatitis. This is due to the development of dysproteinemia in these diseases. Changes in the test results are detected in malaria, mononucleosis, typhoid fever.
Treatment of abnormalities
Even a slight increase in the result of the thymol test should alert the attending physician (therapist, gastroenterologist, toxicologist, infectious disease specialist). A change in the properties of proteins and a violation of the ratio of protein components in the blood is an indicator of inflammatory processes. In combination with the assessment of clinical manifestations, other biochemical parameters and data from instrumental research methods, the doctor may consider it necessary to urgently hospitalize the patient in the infectious diseases department.