Background: The uptake of chlamydia screening recommendations for sexually active young women in the USA is debated. The coverage estimates derived from direct (e.g. testing activity) and indirect sources (e.g. surveillance reports) are conflicting, ranging from 14 to 60%.
Methods: We collated US data about chlamydia prevalence (NHANES), surveillance case reports (CDC), chlamydia testing (MarketScan, HEDIS), test positivity and performance (Baltimore City Health Department) and sexual activity (NSFG, NHANES, HEDIS) for 15-25 year old women in 2008. We described the relationships between data sources in a common underlying Bayesian model fitted jointly to the data. This approach simultaneously integrates all the evidence available into parameter estimation. We obtained posterior means (with 95% credible intervals, CrI) for chlamydia testing coverage in sexually active women and all other model parameters.
Results: The model estimates were highly consistent with observed data from surveillance case reports, chlamydia testing, positivity and prevalence, increasing confidence for other parameter estimates. The estimates of chlamydia test coverage were 17.6% (95% credible interval, CrI: 17.1, 18.2%) in sexually active 15-19 year old women and 21.2% (95% CrI: 20.6, 21.9%) in 20-25 year olds. Among women who met HEDIS administrative criteria for sexual activity (53% (95% CrI: 51.4%, 54.7%) of all sexually active women), coverage estimates were 38.3% (95% CrI: 38.1, 38.5%) for 15-19 year olds and 46.2% (95% CrI: 46.1, 46.3%) for 20-25 year olds. Women with chlamydia were considerably more likely to be tested for chlamydia infection than uninfected women (mean 6.0, 95% CrI: 3.1, 9.4).
Conclusions: This model reconciled apparent inconsistencies between data on population chlamydia prevalence and surveillance of diagnosed chlamydia. Overall chlamydia test coverage was lower than expected from some routine data sources. These findings suggest that chlamydia tests are appropriately targeted to women at high risk of chlamydia infection.