Background: Use of nucleic acid amplification tests (NAATs), such as strand displacement assay (SDA, BD ProbeTec™ C.trachomatis / N.gonorrhoeae Amplified DNA Assay), for the detection of gonococcal infection in the community is controversial because of the possibility of false positive results in low prevalence populations.
Aim: To evaluate if culture confirmation of gonococcal infection can be improved for subjects found to be positive by BD ProbeTec in community clinics.
Methods: Two cervical swabs were collected for culture to confirm NAAT positive results in women age over 16, a majority of whom were <25 years and asymptomatic. One swab (UTP) was urgently transported and processed in the laboratory within two hours whereas the other swab (RTP) was stored at 40 C, transported at room temperature and processed 4-72 hours after collection depending on the time and day of collection.
Results: 56 subjects with NAAT positive results were recruited into the study.
Nine (16.1%) subjects who were culture negative were excluded from final analysis due to prior antibiotic treatment (4/9) or the culture having been taken more than one month after the NAAT was positive (4/9) or an incorrect specimen being received (1/9). Overall, 41/47 (87.2%) NAAT positive subjects were confirmed by culture. 40/47 (85.1%) UTP swabs and 27/47 (57.4%) by RTP were positive respectively (p<0.05).
Conclusion: This study shows that culture confirmation in NAAT positive subjects in a community gonococcus screening programme can be significantly improved by urgent transportation to and processing of specimens in the laboratory.