When syphilis is suspected, doctors prescribe a blood test for antibodies to the cardiolipin antigen. This assay is an improved version of the Wasserman (RW) reaction. In its classic form, the RW test has not been used for about 30 years. Nowadays, this study is carried out exclusively by immunological methods. What are the normal values for this test? And how to correctly decipher its results? We will consider these issues in the article.
What is this?
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 the early diagnosis of this dangerous sexually transmitted disease. It allows you to identify the pathology in the early stages.
Venous blood is taken for examination and mixed withcardiolipin antigen. The reaction of interaction between the biomaterial and the drug is called microprecipitation (RMP). If a person is he althy, 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 a chancre (painless ulcer) on the skin or mucous membrane. This is an early symptom of syphilis. Typically, antibody production occurs 2-3 weeks after infection.
The "Cardiolipin antigen" kit is used for the test. It is obtained from a bull's heart. The 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 when reacting with the blood of a patient with syphilis.
Indications
An analysis with cardiolipin antigen is prescribed in the following cases:
- if the patient has unprotected sexual contacts with casual partners;
- during household contacts with patients with syphilis;
- with symptoms of the primary and secondary stages of syphilis (chancre, rashes on the body);
- for suspected neurosyphilis (mental and neurological disorders);
- children born to infected women;
- to controleffectiveness of antisyphilitic therapy.
This test is not always informative in advanced (tertiary) forms of pathology. In the later stages of syphilis, antibody production is significantly reduced.
A sample with cardiolipin antigen must be taken during pregnancy. In addition, such a study is required for donors and people who draw up a medical book.
How is the study done?
It is very important to carefully prepare for the analysis. This test often gives false positive results. Two days before donating blood, you must completely exclude:
- drinking alcohol (even low alcohol);
- taking foxglove drugs;
- fatty food.
The analysis should be taken in the morning on an empty stomach. 8-10 ml of venous blood is taken for the study. Test results are usually ready in 1-2 days.
Norma
If the patient does not suffer from syphilis, then his blood does not react with cardiolipin antigen. A negative test result in most cases means that the person is he althy. In the transcript of the test, this is indicated by the sign "-" or "RW-". This is considered normal.
However, even with negative test results, it cannot be completely ruled out that a person is infected with treponema pallidum. After all, antibodies are not produced during the incubation period of pathology. Very weak production of immunoglobulins is also noted in the tertiary form.syphilis. Therefore, if a person with a negative Wasserman reaction has signs of pathology, then the analysis is prescribed again.
Possible deviations
Let's consider the decoding of the analysis. The severity of a positive reaction is indicated in the form with the results of the test with "+" signs. The following test data are considered abnormal:
- "+ " - doubtful result (it is recommended to retake the test).
- "++" - weakly positive reaction.
- "+++" - positive result.
- "++++" - strongly positive test.
What to do if the test with cardiolipin gave 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 reveals the primary stage of syphilis, and in 100% of cases shows the secondary form of the disease. However, positive test results do not always indicate infection with treponema pallidum. Many factors can influence the data of this analysis. They will be discussed further.
False results
Often there are cases when the Wasserman test shows the formation of antibodies, but the person does not suffer from syphilis. A false positive reaction is noted in the following diseases and conditions:
- pregnancy;
- infectious mononucleosis;
- gout;
- diabetes;
- malaria;
- measles;
- scarlet fever;
- brucellosis;
- pneumonia;
- chlamydia;
- mycoplasma infection;
- viral hepatitis;
- tuberculosis;
- malignant tumors;
- thyroiditis;
- autoimmune diseases (systemic lupus erythematosus, scleroderma, rheumatoid arthritis);
- infection with enteroviruses;
- recent vaccination;
- in elderly patients (in 10% of cases);
- alcohol consumption 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, to make an accurate diagnosis, an immunofluorescent blood test is prescribed. It allows you to more reliably detect the presence of immunoglobulins G to pale treponema. A blood test is also carried out by PCR diagnostics. It shows the presence of DNA fragments of pale treponema in the patient. The doctor makes the final diagnosis only on the basis of a comprehensive study.
