Detection of Chlamydia trachomatis in symptomatic and asymptomatic populations with urogenital specimens by AMP CT (Gen-Probe Incorporated) compared to others commercially available amplification assays

Abstract

The present study was designed to evaluate the sensitivity and specificity of AMP CT (Gen–Probe Incorporated, San Diego, CA, USA) on urogenital specimens taken from symptomatic patients and on first void urine (FVU) specimens from asymptomatic patients. In symptomatic patients, 618 specimens from 140 men (140 urethral swabs and 140 FVU) and 202 women (202 endocervical swabs and 136 FVU) were tested by using cell culture, AMP CT and Amplicor Chlamydia trachomatis MWP™ (microwell plate) (Roche Diagnostics, Somerville, NJ, USA) on genital samples, and AMP CT and Amplicor on FVU. A clinical specimen was considered to be truly positive if either the cell culture was positive and/or both AMP CT and Amplicor were positive. In the asymptomatic population, a total of 300 FVU (136 women and 164 men) were tested by four amplification methods, AMP CT, LCx™ (Abbott, Abbott Park, IL, USA), Amplicor MWP, and Cobas Amplicor. A subject was considered to be infected when two or more amplification methods were positive. In the symptomatic population (prevalence 13%), concordant results were observed in 320/342 cases (93.5%). After analysis of discordant results, the sensitivity of AMP CT, Amplicor, and culture was 100%, 95.5%, 68.8%, respectively, and the specificity was 98.3%, 99.3%, 100% respectively. The number of false negative results by AMP CT in urine, probably due to labile inhibitors, was 3/276 (1%). In the asymptomatic population, the results were concordant in 298/300 (99.3%), seven positive and 291 negative. Two results were considered false positives, one by Cobas Amplicor, one by AMP CT. Compared to other amplification methods, AMP CT is at least as sensitive for the identification of chlamydial infection in symptomatic and asymptomatic men and women on genital or urine specimens.