Background:
Researchers have primarily examined chlamydia positivity among women age 15-24 years. However, because positivity is higher among those ages 25-29 than for those over age 29, it is critical to better understand factors that affect positivity among those ages 25-29 to ensure appropriate screening and treatment.

Objective:
We examined chlamydia positivity among women ages 25-29 who were screened for chlamydia during medical visits at Region X Infertility Prevention Project (IPP) STD clinic sites in 2002-2003.

Method:
We used a case-control design in which cases were those who tested positive and controls were those who tested negative. Multivariate logistic regression was used to identify factors differentiating cases and controls.

Result:
Of the 3,696 tests, 6.4% were positive for chlamydia. Measures independently associated with chlamydia were: reason for visit—exposed to chlamydia in the last 60 days, OR=8.3; new sexual partner in the last 60 days, OR=1.4; condom use during last sex, OR=1.6; and one or more clinical findings, OR=2.6.

Conclusion:
Results were generally consistent with other studies. Subjects with clinical findings and those who reported that they were exposed to chlamydia were significantly more likely to have chlamydial infection. In contrast to other studies, subjects who reported that they did not use a condom during last sex, those who reported that they had a new sexual partner in the last 60 days, and those of Hawaiian/Pacific Islander and American Indian/Alaska Native race also were more likely to test positive for chlamydia.

Implications:
Findings suggest that additional studies are needed to determine if condom used during last sex should be included in the Region X IPP female selective screening criteria for those ages 25-29. Furthermore, findings support current interest in the role of sexual network dynamics, need for better information on female clients' sexual behaviors/practices and partners, and the importance of exploring racial/ethnic disparities in disease.