Comparison of the cobas 4800 CT/NG Test with Culture for Detecting Neisseria gonorrhoeae in Genital and Nongenital Specimens in a Low-Prevalence Population in New Zealand
JOURNAL OF CLINICAL MICROBIOLOGY
Authors: Bromhead, Collette; Miller, Amanda; Jones, Mark; Whiley, David
To assess the clinical utility of replacing microbial culture for Neisseria gonorrhoeae with a nucleic acid amplification test (NAAT), we compared N. gonorrhoeae culture with the cobas 4800 CT/NG test for 18,247 urogenital and 666 nongenital samples. For urogenital specimens, the sensitivity, specificity, and positive and negative predictive values of the cobas N. gonorrhoeae PCR were 98.7%, 100%, 95.6%, and 100%, respectively, and for nongenital specimens, the values were 100%, 99.8%, 92.9%, and 100%, respectively. In our test population, 37% (10,185) of patients tested over the study period were screened for C. trachomatis by PCR but were not screened for gonorrhea by culture. Of these, 43 were N. gonorrhoeae positive by PCR and therefore went undiagnosed. The cobas 4800 CT/NG test diagnosed 33% (n = 30) more urogenital and 25% (n = 3) more rectal gonorrhea infections than culture and, based on the above performance indicators, does not require supplementary testing for urogenital or rectal specimens. The ability to test noninvasive specimens (such as urine and self-taken vulvovaginal swabs) for N. gonorrhoeae will enable more patients to be screened for infection, thus offering significant positive public health benefits.
Accuracy of Presumptive Gonorrhea Treatment for Gay, Bisexual, and Other Men Who Have Sex with Men: Results from a Large Sexual Health Clinic in Los Angeles, California
Authors: Shover, Chelsea L.; Beymer, Matthew R.; Unger, Erin M.; Javanbakht, Marjan; Bolan, Robert K.
Purpose: This study analyzed the accuracy of presumptive gonorrhea treatment in a sexual health clinic serving primarily gay, bisexual, and other men who have sex with men (MSM). Treating suspected gonorrhea before laboratory confirmation can reduce symptoms and transmission; however, this strategy can overtreat uninfected individuals, which may promote antimicrobial resistance. We identified differences in accuracy of gonorrhea presumptive treatment by site of infection and presence of signs or symptoms. Methods: We conducted a cross-sectional study of gay, bisexual, and other MSM who were treated presumptively for gonorrhea at the Los Angeles LGBT Center between February and July 2015. We calculated positivity of treated patients, proportion of infections treated, and positive predictive value (PPV) of treating gonorrhea presumptively based on signs, symptoms, or exposure at the urethral, rectal, or pharyngeal site. Results: Of 9141 testing visits, presumptive treatment was provided at 1677 (18%). Overall, gonococcal infections were identified at 31% (n = 527) of visits where presumptive treatment was provided, compared to 9% (n = 657) of visits without presumptive treatment (P < 0.01). Forty-five percent of gonococcal infections were treated presumptively, and treatment was provided at 14% of gonorrhea-negative visits. Seventy-eight percent of urethral, 54% of rectal, and 35% of pharyngeal infections were treated presumptively. PPV was highest for genitourinary signs. Conclusion: Approximately one-third of gay, bisexual, or other MSM treated presumptively for gonorrhea at a sexual health clinic tested positive for gonorrhea. These findings highlight the potential contribution of point-of-care tests in reducing overtreatment resulting from presumptive treatment.