Author(s): Barbara Van Der Pol 1
Chlamydia trachomatis; laboratory automation; molecular diagnostics; Neisseria gonorrhoeae; sexually transmitted infections
Chlamydia trachomatis and Neisseria gonorrhoeae (CT/NG) remain highly prevalent sexually transmitted infections. The most recent WHO estimates of annual cases were 98 and 31 million for chlamydia and gonorrhea, respectively  . This translates into prevalence estimates for people aged 15-49 years of 3.5 and 2.2% in women and men, respectively, for chlamydia and 1.02 and 0.79% for gonorrhea  . These estimates are supported by data collected from various settings globally [2-4] . Of note, in these various studies, 66.7-100% of those identified with infections reported no symptoms, thus demonstrating the need for asymptomatic screening programs. While gonorrhea rates are substantially lower than chlamydia rates, the occurrence of coinfections is common, which suggests that, if affordable, gonorrhea screening may be clinically relevant in certain settings [4,5] .
Recommendations for routine screening for infection with C. trachomatis exist in many countries; these recommendations usually focus on women 25 years of age and younger, and on individuals with multiple sexual partners [6,7,102,103] . In the USA, this also includes a recommendation for screening these women for N. gonorrhoeae at the same time  . Provision of screening services is enhanced by the use of highly sensitive nucleic acid amplification tests (NAATs)  . Currently, several NAATs are commercially available that have excellent sensitivity and specificity for C. trachomatis and most NAATs also provide available N. gonorrhoeae testing with excellent sensitivity [8-24] . Sensitivity for all assays is estimated to be above 90% while specificity is above 95%. Attention should be given to the information in the package insert to determine whether the gonorrhea assay is specific for N. gonorrhoea e or has the potential to amplify closely related nongonococcal species that may be commensal.
One caveat with NAATs for chlamydia is the inability of certain first-generation assays to detect the new variant of C. trachomatis (nvCT) that was first observed in Sweden [25,26] . The nvCT strain contains a deletion mutation in the primer binding region targeted by the Amplicor assay (Roche Diagnostics, IN, USA). Newer assays have been developed to include duplicate target regions in order to detect this strain of chlamydia.
In summary, many commercially available NAATs have excellent performance characteristics. Increases in sensitivity are unlikely to be necessary in new assays given that current methodologies can detect sufficiently low numbers of DNA copies that positive results may reflect exposure to organisms rather than actual infections. Thus, the clinical relevance of any increase in sensitivity is unclear. As a result, new assays must focus on achieving sensitivity similar to currently available assays, improving specificity, particularly for N. gonorrhoeae , use of dual targets in order to detect strain variations, improved clinical and patient convenience and improved laboratory efficiency. This review provides information about the new cobas® 4800 (c4800) CT/NG assay and will touch on each of these points. There are limited published data of evaluations of the performance of this system due to the recent regulatory approval in most settings. The...