Chlamydia trachomatis: screening programs and the nucleic acid amplification assays

Abstract

Methods using the artificial amplification of nucleic acids or signals after hybridization are a new advantage in the diagnosis of genital infections with Chlamydia trachomatis. Commercially available nucleic acid amplification (NAA) assays have provided laboratories with powerful tools having a particular impact in the detection of genital chlamydial and gonococcal infections. Compared with cell culture methodologies and other techniques, NAA assays such as ligase chain reaction (LCR), polymerase chain reaction (PCR), and transcription-mediated amplification (TMA) have shown a performance pattern with a higher sensitivity for invasive and noninvasive sample types and a high specificity when compared with culture. This means that enzyme immunoassays (EIAs) and immunofluorescence techniques, used for many years for the routine diagnosis of genital chlamydial infections, are now more and more substituted by NAA assays. Similar to the performance of chlamydial diagnosis, the codetection of a genital infection with Neisseria gonorrhoeae (N. gonorrhoeae) has shown a high sensitivity and specificity using NAA assays on both male and female specimens. Gonococcal cultures when performed under optimal conditions show a sensitivity comparable with NAA assays and may even surpass their specificity owing to problems of some amplification tests with the reproducibility of positive results and with antibiotic resistance proof. Limitations of NAA assays may still be the high costs of their performance in laboratories. Furthermore, problems with inhibition of amplification and contamination under certain conditions may lead to reduced reproducibility of positive and negative results. Collection, transport, and storage of samples are of importance and have shown to influence the results even when using amplification techniques. An important advantage is the fact that NAA assays offer reliable results on noninvasive samples not only in symptomatic patients but also in asymptomatic individuals and therefore allow the performance of large-scale, community-based and setting-based screening programs. Community-based urine testing by NAA assays successfully identified chlamydial infections in different risk groups and was well accepted by community members. Studies have been performed in female and male military recruits, in asymptomatic men and women, in high school students, in pregnant women, and in other population groups of special importance for chlamydial diagnosis. The screening for C. trachomatis can significantly influence chlamydial epidemiology by facilitating early detection, treatment, and interruption of transmission.