Detection of Neisseria gonorrhoeae and Chlamydia trachomatis by PCR in a sample pool (urine, rectum and pharynx) in asymptomatic patients at risk of sexually transmitted infections

Introduction

Detection of Neisseria gonorrhoeae (NG) and Chlamydia trachomatis (CT) is periodically indicated in asymptomatic patients with risky sexual practices. The objective of this study was to assess the efficacy of employing a rapid polymerase chain reaction (PCR) test in a combined pool of three samples from the same patient and compare it with the standard PCR performed in the three different samples separately.

Methods

Samples were collected from asymptomatic patients at risk of sexually transmitted infections (STI). Urine samples, two pharyngeal swabs, and two rectal swabs were collected from each patient. Two PCR techniques were performed: standard PCR (Allplex CT/NG/MG/TV®, Seegene) in each of the three samples separately, and rapid PCR (Xpert CT/NG®, Cepheid) in a pool of three samples.

Results

A total of 429 pooled samples from 403 patients were included in the study, and 426 urine samples, 412 rectal swabs and 426 pharyngeal swabs were also processed. Concordances between pooled and individual PCRs for both CT and NG identification were 94.17%, with 77 (17.9%) positive samples. The concordance for CT was 98.60%, with 38 positive samples (8.88%), being 95.33% for NG, with 51 positive samples (11.88%).

Conclusion

The use of a pool of three samples (urine, rectum and pharynx) for the detection of NG and CT using rapid PCR can be a cost-effective alternative to performing conventional PCR in the three samples separately in asymptomatic patients at risk of developing STI.