Don’t be “fooled” by the syphilis test sheet

　　Syphilis is caused by Treponema pallidum sexually transmitted diseases . After being infected with syphilis, two types of antibodies will be produced in the human body, one is directly against Treponema pallidum, and the other is against lipids. Antibodies against lipids are not specific because they do not directly target Treponema pallidum. In addition to those infected with syphilis, patients with other diseases disease As well as changes in physiological conditions, low-titer anti-lipoid antibodies may also be produced in the body.

　　Professor Wang, 60 years old, suffers from severe coronary heart disease , prepare for hospitalization. Before admission, the doctor conducted a comprehensive examination on Professor Wang, including a serological test for syphilis. The test report came out, and it clearly said: RPR (a syphilis screening test) was positive, with a titer of 1:4; TRHA (a syphilis confirmation test) was positive. This was like a bolt from the blue. Professor Wang, who had a very strict attitude towards life, could not figure out when he was infected with syphilis.

　　The news quickly spread in the college, and the rumors brought a heavy mental burden to Professor Wang. What worries him even more is that if he really has syphilis, will his wife be infected? There is nothing better than a wife who knows her husband. Mrs. Wang knows her husband very well for decades. She does not believe the test results in front of her and advises her husband to go again. Hospital Inspections and consultations.

　　I received them warmly, carefully inquired about Professor Wang's life history and past medical history, conducted a careful physical examination, and also conducted a syphilis test for Mrs. Wang. During the physical examination, no swollen superficial lymph nodes in the groin or other parts of the body were found in the two elderly people, and there was no evidence of syphilis. skin damage. Mrs. Wang’s syphilis test result was negative. After comprehensive analysis, I concluded decisively: Professor Wang did not suffer from syphilis, and the syphilis test result was a false positive.

　　Why do syphilis tests show false positives?

　　Syphilis serology test is an important basis for diagnosing syphilis, but it is not the only basis. Diagnosing syphilis, in addition to laboratory test results, is more importantly based on a detailed understanding of the patient's life history and past medical history, as well as a detailed physical examination. Only by making careful judgments after comprehensive analysis can we avoid misdiagnosis caused by false positive syphilis test results.

　　When diagnosing syphilis, the syphilis serology test tests for these two types of antibodies. The RPR test mentioned earlier is an experiment to detect lipid-like antibodies; while TPHA is an experiment to directly detect Treponema pallidum. Because RPR is an experiment that detects lipid-like antibodies rather than directly detecting anti-Treponema pallidum antibodies, it is non-specific. Any disease that can cause the production of lipid-like antibodies can make RPR positive. In addition to syphilis, respiratory infections, pneumonia, active tuberculosis, rheumatic heart disease, subacute bacterial endocarditis, infectious hepatitis, cirrhosis, chronic nephritis, leptospirosis, leprosy, malaria, rheumatoid arthritis, systemic lupus erythematosus and heroin addiction can all lead to positive RPR.

　　RPR positivity caused by causes other than syphilis has a characteristic, the titer is generally low, less than 1:8. The RPR test is prone to false positives, and doctors often perform a highly specific TPHA test at the same time to confirm the diagnosis of syphilis. It is worth mentioning that TPHA and other specific tests that directly target Treponema pallidum have a false positive rate of 1% in the general population. It has been reported in China that half of the inpatients in the internal medicine department of a certain hospital who were TPHA positive were false positives. Diseases known to cause TPHA positivity include: rheumatoid arthritis, lupus, diabetes, colon cancer, lymphosarcoma, hepatitis C, cirrhosis, AIDS, leprosy, genital herpes, heroin addiction, etc.

　　In addition to diseases, changes in certain physiological conditions, such as pregnancy, can also lead to positive RPR and TPHA. It is particularly worth mentioning that, elderly The false positive rate of syphilis serological examination is higher than that of the general population, and it has been reported that it can reach 2%. Many older adults suffer from common medical illnesses that can also lead to a positive syphilis test. Not long ago, a domestic hospital reported that five elderly patients aged 63 to 80 years old with medical diseases they admitted were suffering from coronary heart disease, cerebrovascular disease, diabetes and leukemia. During their hospitalization, they all had positive RPR and TPHA.

　　Experts remind syphilis patients that misdiagnosis of syphilis is rare after all. In most cases, everyone still needs to go to the hospital for examination so that they can receive timely treatment.