Decreases in Rates of Reported Chlamydia Among Females — United States, 2011–2013

BACKGROUND:   Sexually transmitted chlamydial infections are usually asymptomatic, but, left untreated, can lead to serious reproductive health outcomes. Consequently, routine screening is recommended for sexually-active women aged <25 years. When national reporting began, rates of reported cases of chlamydia increased steadily, likely due to increases in reporting completeness and expanded screening efforts. For the first time, the national case rate decreased during 2012–2013, primarily among young women. We explored factors which may have impacted reported case rate trends in recent years.

METHODS:  We examined rates by patient demographics, diagnosing provider type (e.g., health department clinic, private provider), and jurisdiction during 2011–2013. We reviewed chlamydia screening data submitted to the Healthcare Effectiveness Data and Information Set (HEDIS) collected among females aged 16–20 years and 20–24 years in commercial and Medicaid health plans.

RESULTS:  During 2011–2013, rates of reported chlamydia decreased 2.4% among all women (644 to 623 per 100,000).  Rates decreased 12.7% (3,299 to 3,043 per 100,000) among females aged 15–19 years, were similar among females aged 20–24 years (3,630 to 3,621 per 100,000; 0.2% decrease), and increased 3.8% among females aged 25-44 years (564 to 611 per 100,000). Among 15–19 year old females, rates decreased in 37 states and the District of Columbia and decreased among all provider types. Among health plans reporting to HEDIS, the proportion of 16–20 year olds screened in commercial health plans remained stable during 2011–2013 (41.5% to 41.1%) and decreased slightly among females in Medicaid plans (54.9% to 51.3%). Among 20–24 year olds, the proportion screened in commercial plans increased (48.4% to 50.2%) and decreased in Medicaid plans (63.4% to 61.4%).

CONCLUSIONS:  National decreases in reported case rates of chlamydia among females in recent years are unlikely due to changes in reporting, as decreases were seen only among 15-19 year olds and were observed for multiple provider types and in the majority of jurisdictions. Decreases in screening among the Medicaid population may have affected the number of infections identified; however, it is unlikely that decreases in screening completely explain observed decreases in case rates. Nonetheless, more information on population screening coverage, including estimates among young women not covered by health plans, is needed to fully understand the impact of screening on case rates. State and local jurisdictions, where more detailed screening data may be available, should examine factors impacting chlamydia trends in their areas.