Clinical evaluation of an automated enzyme-linked fluorescent assay for the detection of chlamydial antigen in specimens from high-risk patients

Abstract A fully automated enzyme-linked fluorescent assay (ELFA) on the Vitek Immunodiagnostic Assay System (VIDAS CHL) was evaluated for the detection of chlamydial antigen in specimens from symptomatic and asymptomatic high-risk patients. The results were compared with those from McCoy cell culture and Chlamydiazyme with a blocking assay. False-positive VIDAS specimens were centrifuged and the pellet stained with direct fluorescent antibody (DFA). Of the 158 urine specimens, 52 (33%) were infected by Chlamydia trachomatis . The sensitivity and specificity of the VIDAS when compared with cell culture, DFA, and Chlamydiazyme were 75% and 96%, respectively, for urine specimens while the predictive value of a positive (PVP) and a negative (PVN) were 91% and 88%, respectively. Of the 245 urethral swabs, 75 (31%) were considered positive. The sensitivity and specificity were 71% and 92%, respectively, and the PVP and PVN were 80% and 87%, respectively. The sensitivity and specificity on the 108 cervical swabs, 22 of which were positive, were 95% and 95%, respectively, and PVP and PVN were 88% and 99%, respectively. Compared with Chlamydiazyme, the VIDAS was more sensitive on specimens from female patients and urine specimens, but less sensitive on urethral specimens from male patients.