Evaluation of an IgG cystatin capture enzyme-linked immunosorbent assay for the detection of anti-cysteine proteinase antibodies in asymptomatic trichomoniasis patients.

All isolates of T. vaginalis release cysteine proteinases proteolytic enzymes that are shed into the vagina or culture medium. Cystatin has been used successfully as a capture agent in ELISA to detect cysteine proteinase antibodies without the need for purified proteinases. The ELISA was evaluated in comparison to wet mount microscopy and culture techniques. IgG cystatin capture ELISA proved to be a sensitive and highly specific (100%) assay that could rapidly detect anti-cysteine proteinase antibodies in both vaginal washouts and sera of asymptomatic patients with a sensitivity of 100% and 86.7%, respectively. A defined discrimination between sero-positive and sero-negative individuals was markedly observed for ELISA-vaginal washouts providing a more conclusive diagnosis by this technique. The results demonstrated that in trichomoniasis patients (52 cases) whether symptomatic or asymptomatic. T. vaginalis infection was detected in 19 (36.5%), 49 (94.2%), 50 (96.1%) and 48 (92.3%) by wet mount, culture, cystatin capture ELISA-vaginal washouts and ELISA-sera, respectively. The assay was reliable also as a test of cure with a specificity of 94.4% in the vaginal washouts and 83.3% in sera.