Conventional culture versus nucleic acid amplification tests for screening of urethral Neisseria gonorrhea infection among asymptomatic men who have sex with men

BACKGROUND Many methods are used to detect urethral Neisseria gonorrhea (NG) infection among asymptomatic men who have sex with men (MSM). The objective of this study was to define the performance of conventional culture compared to real-time polymerase chain reaction (PCR) for diagnosis of asymptomatic urethral gonorrhea among MSM. METHODS In this cross-sectional study, 147 clinical specimens for NG testing from asymptomatic participants were evaluated. MSM >18 years old who consented to undergo urethral swab and collection of urine samples from two clinics (one was the sexually transmitted diseases (STDs) mobile clinic and the second was the antiretroviral clinic) located in Khon Kaen, Thailand, were recruited. For conventional culture, 147 swab specimens from urethra were analyzed. For real-time PCR, the same samples and collected urine (147 urethral swab and 62 urine) were evaluated. RESULTS Participants were predominately older aged (mean age: 28.79 years, range: 18-54), asymptomatic (99.3%), and engaged in sex with multiple partners (63% had at least two partners and 36% had at least three partners during the previous 3 months). Twenty-five MSM (17%) had history of STD, mainly human immunodeficiency virus infection. Of the 147 specimens, 42 were positive for NG detected by real-time PCR (prevalence: 28.6%, 95% confidence interval [CI]: 24.8%-32.4%), while none of the 147 MSM were positive for NG detected by conventional culture (prevalence: 0.0%, 95% CI: 0.0%-7.3%). These findings indicated that conventional culture had low sensitivity but high specificity (0.0% and 100%, respectively). We could not demonstrate that many of the factors that were identified in other studies were associated to increased (or decreased) risk of urethral gonococcal infection in our population. CONCLUSION In asymptomatic MSM, nucleic acid amplification tests are more appropriate for screening of urethral NG infection than conventional culture. However, the culture method is necessary for monitoring emerging antimicrobial resistance and to inform gonorrhea treatment guidelines.