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Condom effectiveness for reducing transmission of gonorrhea and chlamydia: the importance of assessing partner infection status.
American Journal of Epidemiology 2004;159(3):242-251.
Warner L, Newman DR, Austin HD, Kamb ML, Douglas JM, Malotte CK, Zenilman
JM, Rogers J, Bolan G, Fishbein M, Kleinbaum DG, Macaluso M, Peterman
TA for the Project RESPECT Study Group.
Abstract
This analysis examined the importance of differential exposure to infected
partners in epidemiologic studies of latex condom effectiveness for prevention
of sexually transmitted infections. Cross-sectional, enrollment visit data
were analyzed from Project RESPECT, a trial of counseling interventions conducted
at five publicly funded US sexually transmitted disease clinics between 1993
and 1997. The association between consistent condom use in the previous 3
months and prevalent gonorrhea and chlamydia (Gc/Ct) was compared between
participants known to have infected partners and participants whose partner
infection status was unknown. Among 429 participants with known Gc/Ct exposure,
consistent condom use was associated with a significant reduction in prevalent
gonorrhea and chlamydia (30% vs. 43%; adjusted prevalence odds ratio = 0.42,
95% confidence interval: 0.18, 0.99). Among 4,314 participants with unknown
Gc/Ct exposure, consistent condom use was associated with a lower reduction
in prevalent gonorrhea and chlamydia (24% vs. 25%; adjusted prevalence odds
ratio = 0.82, 95% confidence interval: 0.66, 1.01). The number of unprotected
sex acts was significantly associated with infection when exposure was known
(p for trend < 0.01) but not when exposure was unknown (p for trend =
0.73). Restricting analyses to participants with known exposure to infected
partners provides a feasible and efficient mechanism for reducing confounding
from differential exposure to infected partners in condom effectiveness studies.