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Syphilis: passive hemagglutination reaction
Medical expert of the article
Last reviewed: 06.07.2025
Treponemal antibodies are not normally detected in blood serum.
RPGA based on gel technology is used to detect specific treponemal antibodies. The sensitivity and specificity of the test for primary syphilis are 76 and 99%, respectively, for secondary syphilis - 100 and 99%, for late syphilis - 94 and 99%, for latent syphilis - 97 and 99%. RPGA is used as a confirmatory test for syphilis and to exclude false positive results obtained in the microprecipitation reaction.
The results of the RPGA study are expressed in titers, they can be used to evaluate the treatment, but they are significantly inferior to the microprecipitation reaction in this aspect. RPGA uses sensitized erythrocytes, so 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 non-specific antibodies in the patient's serum).