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Is yearly screening for Chlamydia worthwhile?

Reuters Health • The Doctor's Channel Daily Newscast

EW YORK (Reuters Health) – Annual testing for Chlamydia trachomatis doesn’t prevent many cases of pelvic inflammatory disease (PID), according to a prospective U.K. study published in BMJ Online First on April 9.

“The cost effectiveness of screening might be exaggerated,” the researchers say. They add, “Policy makers might consider focusing on more frequent testing of those at higher risk, such as women with a new sexual partner or a recent history of chlamydial infection.”

For the Prevention of Pelvic Infection (POPI) trial, Dr. Pippa Oakeshott from the University of London and associates recruited 2529 sexually active young women from colleges and universities in London. Participants completed brief questionnaires on sexual health and provided vaginal swabs.

The researchers randomly assigned the women to have their samples immediately tested (with referrals to general practitioners offered in case of chlamydial infection) or to have their samples frozen and analyzed a year later (deferred screening controls).

The baseline prevalence of chlamydia was 5.4% in immediately tested women and 5.9% in controls.

Among the 2377 women followed up after 12 months, the incidence of PID was 1.3% in immediately screened subjects and 1.9% in controls, a nonsignificant reduction of 35%.

Among the 137 women with chlamydial infection at baseline, 1 of 63 (1.6%) screened subjects and 7 of 74 (9.5%) deferred subjects developed PID during follow-up (p = 0.07). However, 30 of the 38 cases of PID (79%) were in women who originally tested negative for Chlamydia.

Dr. Oakeshott’s group estimates that prevention of one clinical case of PID over 12 months would require screening 147 women for chlamydial infection or treating 13 women who test positive.

They suggest that Chlamydia was probably acquired after screening by many of the women.

In an editorial, Dr. Jessica Sheringham from University College London counters that the inability of chlamydial screening to prevent PID may be because chlamydia infection was not the primary cause of PID in those women.

She adds that if England’s national screening program is carried out as intended, with “tests…accompanied by sexual health advice and, after a positive result, by treatment of the current sexual partner,” it has the potential to also reduce the overall prevalence of Chlamydia.

BMJ 2010.