If syphilis is suspected, doctors prescribe a blood test for antibodies to the cardiolipin antigen. This analysis is an improved version of the Wassermann reaction (RW). In its classic form, the RW test has not been used for about 30 years. Today, this study is carried out exclusively by immunological methods. What are the normal rates of this sample? And how to decipher its results? We will consider these issues in the article.
What it is?
Cardiolipin antigen is a lipid-like substance. In its composition, it is similar to the proteins of the causative agent of syphilis - pale treponema. Such a drug is used for early diagnosis of this dangerous sexually transmitted disease. It allows you to identify pathology in the early stages.
Venous blood is taken for the study and mixed with the cardiolipin antigen. The reaction of the biomaterial and the drug is called microprecipitation (RMP). If a person is healthy, then his blood does not produce antibodies to the antigen. If the patient suffers from syphilis, then class M and G immunoglobulins are actively formed in his body. In this case, flakes appear in the mixture of blood and the drug. This precipitate is an accumulation of antigen-antibody complexes (precipitate).
The formation of immunoglobulins in an infected person begins 7-10 days after the appearance of chancre (a painless ulcer) on the skin or mucous membrane. This is an early symptom of syphilis. Usually, antibody production is observed 2–3 weeks after infection.
For the test, use the cardiolipin antigen kit. It is obtained from a bull’s heart. Organ extract is mixed with cholesterol and lecithin. The resulting substance has similar properties to the proteins of pale treponema. It can cause the formation of immunoglobulins in the reaction with the blood of a patient with syphilis.
Indications
An analysis with cardiolipin antigen is prescribed in the following cases:
- in the presence of unprotected sexual contacts of the patient with random partners;
- at household contacts with patients with syphilis;
- with symptoms of the primary and secondary stages of syphilis (chancre, rashes on the body);
- with suspected neurosyphilis (mental and neurological disorders);
- children born to infected women;
- to monitor the effectiveness of antisyphilitic therapy.
This test is not always informative with advanced (tertiary) forms of pathology. In the later stages of syphilis, antibody production is substantially reduced.
A test with cardiolipin antigen must be given during pregnancy. In addition, such a study is required to go through to donors and people who draw up a medical book.
How is the study conducted?
It is very important to carefully prepare for the analysis. This test quite often gives false positive results. Two days before blood donation, you must completely exclude:
- drinking alcohol (even low alcohol);
- taking drugs with digitalis;
- greasy food.
Analysis should be taken in the morning on an empty stomach. For the study take 8-10 ml of venous blood. Test results are usually ready in 1-2 days.
Norm
If the patient does not suffer from syphilis, then his blood does not react with the cardiolipin antigen. A negative test result in most cases means that the person is healthy. In the decoding of the test, this is indicated by the sign "-" or "RW-". This is considered the norm.
However, even with negative test results, it cannot be completely ruled out that a person is infected with pale treponema. After all, antibodies are not produced during the incubation period of the pathology. Very weak production of immunoglobulins is also noted in the tertiary form of syphilis. Therefore, if a person with a negative Wasserman reaction has signs of pathology, then the analysis is prescribed again.
Possible deviations
Consider a breakdown of the analysis. The severity of a positive reaction is indicated on the form with the results of the test by the signs "+". The following test data are considered deviations from the norm:
- "+" - a dubious result (it is recommended to retake the analysis).
- "++" is a weakly positive reaction.
- "+++" is a positive result.
- "++++" is a sharply positive test.
What to do if a test with cardiolipin gives positive results? The diagnosis of syphilis is usually not made only by the Wasserman reaction. In this case, doctors always prescribe additional studies.
This test in 70% of cases allows you to identify the primary stage of syphilis, and in 100% of cases shows a secondary form of the disease. However, the positive results of the study do not always indicate infection with pale treponema. Many factors can influence this analysis. They will be discussed later.
False results
Often there are cases when a Wasserman test shows the formation of antibodies, but at the same time, a person does not suffer from syphilis. A false positive reaction is noted in the following diseases and conditions:
- pregnancy
- infectious mononucleosis;
- gout
- diabetes mellitus;
- malaria
- measles
- scarlet fever;
- brucellosis;
- pneumonia;
- chlamydia;
- mycoplasma infection;
- viral hepatitis;
- tuberculosis
- malignant tumors;
- thyroiditis;
- autoimmune diseases (systemic lupus erythematosus, scleroderma, rheumatoid arthritis);
- enterovirus infection;
- recent vaccination;
- in patients of senile age (in 10% of cases);
- drinking alcohol on the eve of the study;
- drug addiction.
It can be concluded that the list of diseases and conditions in which false test results are noted is quite extensive. Therefore, an immunofluorescence blood test is prescribed to make an accurate diagnosis. It allows you to more reliably detect the presence of immunoglobulins G to pale treponema. A blood test is also performed by PCR diagnostics. It shows the presence of pale treponema DNA fragments in the patient. The doctor makes the final diagnosis only on the basis of a comprehensive study.