Chlamydia screening failed to reduce pelvic inflammatory disease risk

A screening test for chlamydia may not reduce the incidence of pelvic inflammatory disease in women, according to results of a recently published study.

Pippa Oakeshott, MD, of St. George’s, University of London, and colleagues recruited 2,529 women between the ages of 16 and 27 for the Prevention of Pelvic Infection trial. Participants completed a questionnaire and provided researchers with self-administered vaginal swabs. The swabs were either screened immediately (1,254 women) or stored for one year and then analyzed (1,265 women for controls).

The prevalence of chlamydial infection at baseline was 5.4% among women who were screened immediately and 5.9% among controls. Pelvic inflammatory disease occurred in 1.3% of 1,191 screened women and 1.9% of 1,186 women in the control group (RR, 0.65; 95% CI, 0.34 to 1.22).

Pelvic inflammatory disease occurred most frequently in women who tested negative for chlamydia at baseline, at a rate of 79%. Among 63 women in the screened group who had baseline samples that were positive for chlamydia, 1.6% developed the disease during follow-up (RR, 0.17, 0.03-1.01). Among 74 women in the control group with baseline samples that were positive for chlamydia, 9.5% (95% CI, 4.7% to 18.3%) developed pelvic inflammatory disease during the follow-up period.

The researchers noted that 22% of participants received independent testing for Chlamydia during the follow-up period, which may have reduced the effect of screening and influenced the study results.

“Although some evidence shows that screening reduced rates of pelvic inflammatory disease, especially in women with chlamydial infection at baseline, the absolute number of cases prevented was small,” the researchers wrote.

The researchers wrote that women should be encouraged to get repeat testing each time they have a new sexual partner.

Oakeshott P et al. BMJ. 2010;340:c1642.