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Syphilis: passive hemagglutination reaction
Last reviewed: 19.10.2021
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Treponemal antibodies in serum normally do not determine.
RPGA based on gel technology is used to detect specific treponemal antibodies. The sensitivity and specificity of the test for primary syphilis is 76 and 99%, respectively, for secondary syphilis - 100 and 99%, for late syphilis - 94 and 99%, for latent 97% and 99%. RPHA is used as a confirmatory test for syphilis and to exclude false positive results obtained in the microreaction of precipitation.
The results of the RPHA study are expressed in titers, they can be used to evaluate the ongoing treatment, but they are significantly inferior to the microreaction of precipitation in this aspect. In RPHA, sensitized erythrocytes are used, therefore false positive test results can be obtained in patients with autoimmune diseases (systemic lupus erythematosus), viral infections (due to the presence of a large number of nonspecific antibodies in the serum of patients).