In a number of diseases, sedimentary samples are used for diagnosis. One of them is the thymol test, proposed in 1944 by Maclagan. It is based on a change in the colloidal stability of serum proteins in diseases involving dysproteinemia.
Normally, blood proteins are in a state of high stability. With a change in the ratio of fractions of albumin and globulin, the colloidal stability of proteins decreases. The lower it is, the more proteins precipitate and precipitate when thymol reagent is added.
When conducting the sample, an alcohol solution of thymol in veronal buffer or Tris buffer is used as a reagent. The final chemistry of the reaction is not clear. However, the thymol test clearly correlates with the clinical picture of diseases that occur with dysproteinemia. It is easy to set up and easy to use, so it continues to be widely used in biochemical blood tests.
When staging a sample, the patient's serum is added to the saline solution, then the reagent is added. If normally a thymol sample is accompanied by a very slight loss of protein flakes and a slight clouding of the reaction mixture, then in the case of dysproteinemia, the solution becomes significantly cloudier. The degree of turbidity depends on the degree of violation of the colloidal properties of proteins. The result of the sample increases with a decrease in albumin and an increase in beta and gamma globulins.
The degree of turbidity is measured on a biochemical analyzer or photoelectrocolorimeter. As a reference solution, barium chloride of a certain concentration is used.
This study has particular clinical significance in hepatitis, collagenoses, and other diseases accompanied by dysproteinemia, a violation of the ratio of serum proteins. For liver lesions with hepatitis, an elevated thymol test is characteristic. Its norm is from 0 to 4 units. With hepatitis, it becomes positive a week before jaundice. In some cases, there is an increase in the sample to 20 or more units. At such high rates, it is necessary to repeat the test with diluted 1: 1 serum of the patient and increase the result by 2 times.
Hemolyzed serum is not suitable for sampling. With hemolysis, the destruction of red blood cells, it turns red. In this case, the sample will be overestimated. The analysis should be repeated after a new blood sample from the vein.
The thymol test is overestimated if the serum is lipemic (chylous), cloudy due to the presence of lipids (chylomicrons) in it. The laboratory assistant, conducting a test with such serum, should instead of control the saline solution make a control of the patient's serum diluted with saline.
To avoid chilism, blood for biochemical studies must be donated strictly to an empty stomach. It should be delivered to the laboratory no later than 2 hours after blood sampling. When stored in a refrigerator, whey is suitable for staging a sample for no more than 7 days.
What does increased thymol test mean? The interpretation is as follows: if it significantly exceeds the norm, you can think about liver disease (hepatitis or cirrhosis), kidney disease that occurs with nephrotic syndrome, systemic diseases such as rheumatism, rheumatoid polyarthritis, scleroderma. For one indicator, it is impossible to make a diagnosis. Thymol test should be evaluated in conjunction with other studies. If a liver disease is suspected, at the same time, at least biochemical analyzes should be done on the level of total and direct bilirubin, transaminase, cholesterol, alkaline phosphatase, zinc sulfate or sublimate test.
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