Chlamydia Screening and Pelvic Inflammatory Disease: Insights from Exploratory Time–Series Analyses

BackgroundScreening for chlamydia has been reported to reduce pelvic inflammatory disease (PID) at the individual level. However, information on population-level association (or causality) is scant.PurposeThis study aims to examine the association between chlamydia and gonorrhea screening and PID diagnoses using time–series analyses.MethodsMonthly chlamydia and gonorrhea screening and PID diagnosis rates were extracted for a cohort of 207,695 continuously enrolled privately insured women from January 2001 to December 2006. An autoregressive integrated moving average model was used to examine whether rates of PID diagnoses in a given month were associated with rates of chlamydia and gonorrhea screening in previous months.ResultsMonthly screening rates increased from about 300 to almost 700 per 100,000 for chlamydia and from 250 to almost 650 per 100,000 for gonorrhea, whereas PID diagnosis rates declined during the same period (40–20 per 100,000). Increases in screening rates were associated with decreases in PID diagnosis rates 4 months later. On average, a one-unit (or 10%) increase in the growth of chlamydia and gonorrhea screening rates, separately, in the prior fourth month was significantly associated with a 0.36 (or 3.6%, p<0.05) and 0.32 (or 3.2%, p<0.10) decrease in the growth rate of the PID diagnosis rate, respectively.ConclusionsAlthough analyses such as these cannot prove causality, the results are consistent with the hypothesis that increases in chlamydia and gonorrhea screening coverage can lead to reductions in PID at the population level. A population-level focus offers advantages over individual-level analyses of screening and PID, such as the ability to capture indirect benefits of increased screening.