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

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.