Evaluation of two serological tests for Trichomonas vaginalis infection

Trichomonas vaginalis is a widely prevalent, sexually transmitted protozoan infecting both males and females. Despite its prevalence, little is known about its contribution to the morbidity rates for urogenital-tract infections. Currently accepted diagnostic methods are limited to the demonstration of the organism in fresh material, identification in stained material, or in vitro cultivation of organisms from the urogenital tract. We have evaluated the indirect hemagglutination test and the gel diffusion test for efficacy in detecting antibodies in serum samples drawn from two population groups. Sera from patients attending a vaginitis clinic had a seropositivity rate of 69% by indirect hemagglutination and 34% by gel diffusion. Seropositivity rates among culture-positive patients were 78% with indirect hemagglutination and 43% with gel diffusion. A group of normal female hospital employees showed seropositivity rates of 30% by indirect hemagglutination and 3% by gel diffusion. Absorption of reactive sera with Trichomonas antigens reduced or abolished the serological reactivity, confirming the specificity of the test. Serological methods can provide a rapid, sensitive, and economical tool to study the epidemiology of this common protozoan infection.