Condom Use and Risk of Gonorrhea and Chlamydia: A Systematic Review of Design and Measurement Factors Assessed in Epidemiologic Studies

Each year, approximately 19 million STD cases occur in the United States. The male latex condom is the contraceptive method most commonly used to prevent STDs. Condoms are highly effective against HIV transmission, epidemiologic research shows. Among serodiscordant couples, recent meta-analyses find consistent condom use reduces HIV risk by at least 80 percent to 94 percent.

However, studies have found less consistent or weaker risk reduction associated with condom use for other STDs. This inconsistency was emphasized in a 2001 National Institutes of Health report and has been used by some to question condoms as an STD prevention strategy. Methodological limitations are often cited for this inconsistency but have not been assessed systematically. In the current study, researchers assessed the importance of four critical design and measurement factors on condom effectiveness estimates with respect to preventing gonorrhea and chlamydia infections.

The authors searched MEDLINE and article biographies to identify English-language, peer-reviewed epidemiologic studies published from January 1966 through April 2005 that evaluated the association between male condom use and risk of either infection. The researchers investigated whether each study distinguished consistent from inconsistent condom use; measured correct use and/or condom use problems; used a design that distinguished incident from pre-existing infection; and selected a study population with documented exposure during the time pertaining to condom use.

Of 45 studies identified, most found condom use was associated with a reduced risk of infection. All the studies had methodological limitations. Only 28 (62 percent) of the studies reviewed distinguished consistent from inconsistent condom use; two (4 percent) reported on correct use or use problems; 13 (29 percent) distinguished incident from prevalent infection; and one (2 percent) included a population with documented exposure to infection. Of the studies that had two or more of the four attributes, eight of 10 reported statistically significant protective effects for condom use compared with just 15 of 35 studies with zero or one attribute (80 percent versus 43 percent, P=0.04).

"Condom use was associated with reduced risk of gonorrhea and chlamydia in men and women in most studies, despite methodological limitations that likely underestimate condom effectiveness," concluded researchers. "Epidemiologic studies that better address these factors are needed to provide a more accurate assessment of condom effectiveness."