Laboratory Tests and Ancillaries
Gonorrhea - Uncomplicated Anogenital Infection_DiagnosticsIf resources permit, lab tests to screen women with vaginal discharge should be considered. Screening for other possible sexually transmitted infections (STIs), including human immunodeficiency virus (HIV), syphilis, and Chlamydia trachomatis, should be done in patients with or at risk of gonorrhea. It is recommended that patients who tested negative within 2 weeks of sexual contact with an infected partner be tested again after this window period if they have not yet received epidemiological treatment.
Please see Chlamydia - Uncomplicated Anogenital Infection disease management chart for further information.
Tests for Neisseria gonorrhoeae
Identification of Neisseria gonorrhoeae at the infected site establishes the diagnosis. Gram-negative intracellular diplococci present in an endocervical smear indicates probable gonorrhea. Gram-negative, oxidase-positive diplococci isolated by culture or N gonorrhoeae demonstrated through antigen or nucleic acid detection confirms gonorrhea.
Microscopic examination of Gram-stained smears of endocervical discharge can be used as an initial test to provide an immediate presumptive diagnosis of gonorrhea. This permits direct visualization of N gonorrhoeae as monomorphic Gram-negative diplococci within polymorphonuclear leukocytes. Microscopic exam of vaginal discharge may be attempted in settings where the Gram stain may be carried out in an efficient manner; however, the sensitivity of the procedure for vaginal discharge specimens is lower compared to urethral specimens in males. A urethral smear is less sensitive than an endocervical smear.
Culture is recommended for pharyngeal and rectal specimens. This readily allows antimicrobial susceptibility testing and monitoring, confirmatory identification, and treatment failure evaluation. This is the only method used to evaluate the efficacy of antibiotic treatment (eg “test of cure”). Specificity and sensitivity are 100% and 61.8-92.6%, respectively. The culture may be negative if obtained <48 hours after exposure. This should be obtained in all cases diagnosed by nucleic acid amplification tests (NAATs) before an antibiotic is given. Culture allows testing of susceptibility and identifying resistant strains. An intracervical swab specimen is more reliable for culture during menstruation.
The nucleic acid amplification test (NAAT) is the most sensitive (>95%) and specific (93.9-100%) test available for Chlamydia trachomatis and Neisseria gonorrhoeae. This is more sensitive than culture, especially for oropharyngeal and rectal sites. This is most useful when patients resist a pelvic exam and may be done at the time of presentation or even <48 hours after exposure. This utilizes a single sample to test for both Chlamydia and gonorrhea. Specimens that may be used are endocervical swabs, urethral discharge, or self-obtained vaginal swabs. The recommended specimen is the self- or physician-obtained vulvovaginal swab.
The routine use of the following lab tests is not recommended: Nucleic acid hybridization or probe test, nucleic acid genetic transformation test, direct fluorescent antibody test, enzyme immunoassay, and serological test. For individuals who have undergone genital reconstructive surgery (GRS), the following specimens may be considered: A Gram-stained smear for microscopy from a bowel segment neovagina; first-pass urine and neovaginal swabs for transgender women; and a vaginal swab if a vagina is still present after GRS as directed by the patient's symptoms and sexual history.