Ans. d. Nucleic Acid Amplification Test (NAAT) Most sensitive investigation for diagnosis in a 25 year old sexually active woman who complains of purulent discharge and dysuria after having intercourse with a new paner (sexually transmitted urethritis) is Nucleic Acid Amplification Test (NAAT). `Gonorrhea and chlamydial infection should be sought by specific tests (e.g., NAATc on the first 10 mL of voided urine). Among dysuric women with sterile pyuria caused by infection with N. gonorrhoeae or C. trachomatis, appropriate treatment alletes dysuria.'-Harrison 18/e p1098 `However, an increasing propoion of men with symptoms and/or signs of urethritis are simultaneously assessed for infection with N. gonorrhoeae and C. trachomatis by 'multiplex' NAAR of first-voided urine. Culture or NAAT for N. gonorrhoeae may be positive when Gram's staining is negative; ceain strains of N. gonorrhoeae can result in negative urethral Gram's stains in up to 30% of cases of urethritis.'- Harrison 18/e p1098 `All men with suspected urethritis should be tested for gonorrhea and chlamydia. The availability of sensitive and specific testing Sexually Transmitted Urethritis Sexually transmitted urethritis can be gonococcal or Non-gonococcal Investigation: PCR: Rapid, specific and sensitive but expensive to use. Multiplex PCR available to detect concomitant T. pallidium, H. ducreyi, HSV infection. Serology: Serological screening for IgM antibodies is useful but presence of elevated levels of IgM antibodies does not differentiate between present and past infection. Recent point of care test based on glycoprotein G has high sensitivity and specificity