Syphilis is a relatively common sexually transmitted disease caused by infection with the syphilis spirochete. The main transmission routes are: sexual contact, blood transmission, and mother-to-child transmission. The diagnosis of syphilis is mainly through the combination of blood tests and clinical symptoms, but most people have some doubts about the results of laboratory tests, now a brief introduction to the problems related to syphilis laboratory tests. Syphilis serological tests mainly include: a. Non-syphilis spirochete antigen test (primary screening test), including VDRL, USR, RPR, TRUST. The significance of the primary screening test: 1. It can be used to observe the efficacy, determine the recurrence and reinfection, and whether it is cured. Early syphilis patients with adequate treatment, reactive elements can disappear, early untreated patients to late, some patients in the reactive elements can also be reduced or disappeared. After treatment, RPR will generally be negative within two years, requiring a serum recheck every three in the first year and every six months in the second year, so that 2-3 years of continuous observation. 2.It is applicable to census, wedding examination, prenatal examination and other health check-ups. There may be biological false positives (titer is often less than 1:8), such as acute febrile infectious diseases, pregnancy, drug addiction, autoimmune diseases (systemic lupus erythematosus, rheumatoid arthritis, etc.). Second, the syphilis spirochete antigen test (confirmatory test), including FTA-ABS, TPHA (TPPA), ELISA. The significance of confirmatory test: the antibody appears earlier than the initial screening time. Sensitivity and specificity are high, for untreated syphilis: 76% for stage I, 100% for stage II, 97% for latent, 94% for late stage. Specificity is 99%. After syphilis treatment, lifelong positivity of this class-causing antibody is generally not negative (but some early syphilis can be negative with effective treatment) and therefore is not used as an indicator of efficacy. There is a certain amount of biological false positives (1%), which are common in SLE, leprosy, etc. Third, the analysis of the results of syphilis serological test: