Incidence rates of pelvic inflammatory disease diagnoses among Army and Navy recruits potential impacts of Chlamydia screening policies.

Background: U.S. Navy policy requires Chlamydia trachomatis screening of all women upon entry to recruit training in conjunction with an educational session, and yearly screening thereafter until age 25. Army policy directs only annual screening of asymptomatic women aged <25. Hence, screening of Army recruits may not occur for up to 12 months following accession. Using routinely collected surveillance data, the rates of outpatient pelvic inflammatory disease (PID) following accession into the Army or Navy were compared to assess the potential implications of these policies.

Methods: The population at risk comprised active-component women aged <25 who accessioned to either the U.S. Army or Navy between January 1, 2001, and December 31, 2005. Subjects were followed up to 60 months from accession, either until a first outpatient PID diagnosis occurred or they departed from military service. Data were collected from 2001 to 2006 and analyzed in 2007. Multiple Poisson regression was used to assess the effects of potentially important covariates. Time-to-event analysis was employed to characterize risk over time.

Results: There were 1276 and 546 incident outpatient diagnoses of PID among 58,088 Army and 33,046 Navy accessions during 93,918 and 65,863 person-years of follow-up, respectively. The crude incident rate was 64% higher in the Army (13.6/1000 person-years) than the Navy (8.3/1000 person-years). Risk for the Army increased soon after accession, followed by a decline, while risk for the Navy remained comparatively uniform.

Conclusions: PID rates were higher in the Army than Navy during the first years of active service. A comprehensive study to elucidate the source of this observed difference is warranted.