Testing for Rectal and Pharyngeal Neisseria Gonorrhea and Chlamydia Trachomatis Infections Among Women — County of San Diego, California, 2008–2009

Background: The Centers for Disease Control and Prevention (CDC) recommends screening of the cervix for women at increased risk for Neisseria gonorrhoea (NG) and Chlamydia trachomatis (CT) infections. The County of San Diego’s (COSD) main STD clinic has been routinely testing women with relevant exposures, regardless of symptom status, for cervical, pharyngeal, and rectal NG and CT infection.

Objectives: To calculate test positivity at each anatomic site; sensitivity of cervical testing for NG or CT infection at any site; and number needed to test (NNT) at all three sites to identify a woman with a pharyngeal or rectal NG or CT infection who did not have a concomitant cervical NG or CT infection.

Methods: We included women tested for NG and CT infection at all three sites during a single visit to COSD’s main STD clinic during January 2008–June 2009. We used nucleic acid amplification tests (Aptima Combo 2, Gen-Probe, Inc., San Diego, CA) to detect NG and CT infection. We calculated NNT as 1/(proportion with an NG or CT infection at any site tested, minus proportion with a cervical NG or CT infection).

Results: Among 362 women, 9 (2%) had any NG infection, with 3 (1%) cervical, 6 (2%) pharyngeal, and 5 (1%) rectal NG tests positive; 29 (8%) had any CT infection, with 13 (4%) cervical, 7 (2%) pharyngeal, and 26 (7%) rectal CT tests positive. Sensitivity of cervical testing for infection at any site was 0.44. NNT was 19.

Conclusions: Sensitivity of cervical testing for NG or CT infection at any site is modest. Because of the low prevalence of NG and CT infection, NNT is high.

Implications for Programs, Policy, and/or Research: Cost-effectiveness of routine testing of women at COSD’s main STD clinic for pharyngeal and rectal NG and CT infection should be assessed.