Research articleUptake of Regular Chlamydia Testing by U.S. Women: A Longitudinal Study
Introduction
Annual screening for Chlamydia trachomatis (chlamydia) is recommended by the CDC for all sexually active women aged ≤25 years1 and for women and men aged 15–25 years by the Royal Australian College of General Practitioners.2 In England, screening is recommended annually and after a change of sexual partner for women and men.3 As stated by the U.S. Preventive Services Task Force, however, the optimal screening interval is not known.4
Chlamydia is the most commonly reported infection in the U.S., with more than 1 million cases notified each year.5 Transmission continues because most infections are asymptomatic,6 the duration of untreated infection is long,7 and young adults change sexual partners frequently.8 Chlamydia infections that ascend to the upper genital tract can cause pelvic inflammatory disease (PID); ectopic pregnancy; and infertility.9 The aims of screening are therefore to detect and treat asymptomatic infection and reduce the incidence of PID.1, 4 Mathematical modeling studies differ in their assumptions but generally assume that all10 or a substantial fixed proportion in the range 35%–65% of women in the target age group receives testing every year.11, 12, 13, 14, 15
The proportion of women who have repeated chlamydia tests every year is not known. Coverage of chlamydia screening is, however, one of the indicators used by U.S. health insurance plans to evaluate the quality of healthcare services (http://www.ncqa.org/).16 The Healthcare Effectiveness Data and Information Set (HEDIS) indicator for chlamydia screening is calculated each year and measures the proportion of women documented as being sexually active, based on use of specific health services and who had a chlamydia test within the past 12 months.17 In 2007 the HEDIS estimate of chlamydia screening coverage was 36% for women aged 16–20 years in commercial health plans.16 Cross-sectional analysis does not show whether the same women are screened every year or if different women are being screened irregularly. Longitudinal analyses of repeated uptake at the enrollee level of preventive services would therefore be useful, and electronic medical records provide an accessible source of data.18 The objective of this study was to determine rates of annual chlamydia testing, as recommended by the CDC, in a cohort of women enrolled in U.S. commercial health plans.
Section snippets
Cohort Construction
The 2002 to 2006 MarketScan databases were used to construct a cohort. The database includes de-identified person-specific data from people enrolled in more than 130 commercial health plans serving more than 100 large employers in all four regions (South, North-Central, West, and Northeast) of the U.S. (http://www.medstat.com/). A unique enrollee identifier is assigned to each individual in the MarketScan claims database by encrypting information provided by data contributors. All women aged
Results
There were 2,632,365 women aged 15–25 years with a continuous period of enrollment of at least 2 days between January 1, 2002, and December 31, 2006 (total follow-up=4,115,444 years, M=1.5 years, SD=1.2; Table 2). The number of women in the cohort increased from 563,926 in 2002 to 989,677 in 2004 and 1,261,082 in 2006. Of all women, 1,985,920 (75.4%) had at least one recorded encounter with a health service. In this group, 321,004 women had 415,072 chlamydia tests. The number of tests increased
Discussion
Among women aged 15–25 years enrolled in commercial health plans from 2002 to 2006, the rate of chlamydia testing overall was 13.6 per 100 woman-years after adjusting the denominator for sexual activity according to the 2002 NSFG. Chlamydia testing rates were lowest in the youngest women. Annual testing rates were low; only 0.1% of women with 5 full years of enrollment were tested in each year, and 74.1% were never tested. Estimated rates of chlamydia testing using the HEDIS measure were
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