Chlamydial infection is the most common bacterial sexually transmitted disease (STD) in the United States, especially among women aged 15 to 24 years.1,2 Because most infections in women are asymptomatic but can progress to serious sequelae,3,4 annual chlamydia screening of sexually active women aged ≤25 years is recommended by several organizations, including the Centers for Disease Control and Prevention (CDC).4 – 7 Despite these recommendations, chlamydia testing rates have been low. Several studies have reported a range of testing rates from 35% to 60%.8 – 12 These testing rates, including screening tests for asymptomatic patients and diagnostic tests for patients with symptoms or signs of chlamydial infection, have been measured for different populations using various data sources and methods, such as survey data for the general population and claims data for insured persons. Using the data from the Healthcare Effectiveness Data and Information Set (HEDIS), a chlamydia testing rate of 41.6% was estimated for sexually active women aged 16 to 25 years who had enrolled in commercial and Medicaid health insurance plans in 2007.9 Another study reported a chlamydia testing rate of 57% for sexually active women aged <25 years who visited federally funded reproductive health clinics.12 An analysis of the 2002 National Survey of Family Growth (NSFG) found a self-reported STD testing rate of 42% for sexually active women aged 16 to 25 years in the United States in 2002, but this estimate was for all STD testing rather than specifically for chlamydia.8
With the addition of an NSFG question to the 2006–2008 survey that asks specifically about chlamydia testing, we estimated the proportion of sexually active US women aged 15 to 25 years who self-reported chlamydia testing in the past year.
We analyzed data from the 2006–2008 NSFG. Details of this survey have been published elsewhere.13,14 Briefly, the 2006–2008 NSFG included a sample of 7356 women aged 15 to 44 years who were interviewed in person from June 2006 through December 2008, with a response rate of 76%. Audio computer-assisted self-interviewing was used to ask sensitive questions during the interview.
Our analysis was performed using data provided by 2944 sampled women aged 15 to 25 years. A woman was considered as sexually active if she answered that she had at least one partner when asked “Thinking about the last 12 months, how many male sex partners have you had in the past12 months? Please count every partner, even those you had sex with only once in those 12 months.” A sexually active woman had a chlamydia test if she answered yes to “In the past 12 months, have you been tested for chlamydia?” Among women who were tested for chlamydia, chlamydial infections were estimated as the number of women who indicated that they had been treated or received medication from a doctor or other medical care provider for chlamydia in the past 12 months. Women were also asked several questions about their use of reproductive health services. Women were classified having a reproductive health service if they reported any health care service in response to 14 questions that were related to contraception, cervical cancer screening, pelvic examination, pregnancy testing, prenatal care, postpregnancy care, abortion, or STD care in the past12 months.
Self-reported chlamydia testing rates were estimated by age, race/ethnicity, health insurance, metropolitan statistical area, and federal poverty level of the respondent's household. To account for the complex sampling design of the NSFG, we used SAS version 9.2 (SAS Institute, Inc., Cary, NC) and SUDAAN version 10.0.1 (Research Triangle Institute, Research Triangle Park, NC) to analyze survey data and generate weighted chlamydia testing rates and standard errors. Bivariate analyses were used to estimate the association of women's characteristics with chlamydia testing. Variables that were significantly associated with testing in bivariate analyses were included in a multivariate logistic regression model, with chlamydia testing as the dependent variable, to estimate adjusted odds ratios and 95% confidence intervals for the associations. In all analyses, a statistically significant difference was defined as a 2-tailed probability of <0.05.
Of 22.6 million women aged 15 to 25 years in the United States, 66.6% (14.8 million) were estimated to be sexually active, ranging from 24.0% of 15 year olds to 89.4% of 25 year olds. Similarly, of those 22.6 million women, 62.1% (12.3 million) reported having a reproductive health service in the past 12 months, ranging from 19.3% of 15 year olds to 82.8% of 25 year olds. Among 14.8 million sexually active women aged 15 to 25 years, 83.1% reported having a reproductive health service in the past 12 months.
Chlamydia testing was reported by 26.2% of all women aged 15 to 25 years, 37.9% of sexually active women aged 15 to 25 years, 41.4% of women aged 15 to 25 years who had reproductive health services in the past 12 months, and 44.8% of sexually active women aged 15 to 25 years who had reproductive health services in the past 12 months (Table 1). Among sexually active women aged 15 to 25 years, chlamydia testing was more likely if they were non-Hispanic black compared with non-Hispanic white, were insured by Medicaid or SCHIP compared with a private insurance plan, had 2 or more sex partners rather than one partner, or had a reproductive health services compared with no reproductive health services in the past 12 months (Table 2). A positivity rate of 9.2% was estimated among women who reported a chlamydia test.
The data that only 37.9% of sexually active women aged 15 to 25 years were tested for chlamydia, and 44.8% of sexually active women aged 15 to 25 years who also had reproductive health services in the past 12 months, confirm findings in other studies of suboptimal chlamydia screening as currently recommended. We also found that the chlamydia testing was significantly associated with women's race/ethnicity, insurance status, sexual behavior, and use of reproductive health services. Although several previous studies have identified interventions that can increase chlamydia testing rates,15 – 17 other barriers, such as high patient cost sharing, need to be resolved.
The self-reported chlamydia testing rate in our study is at the lower end of a range of estimates.9 – 11 Although our estimate of chlamydia testing of sexually active women is similar to the HEDIS estimate, both methods have strengths and weaknesses that impact the estimate. For example, the HEDIS measure may include a greater number of valid chlamydia tests as documented in its claims data compared with the self-reported chlamydia tests in NSFG. On other hand, self-reported sexual activity in NSFG is considered to be a better indicator of women who should be tested. The self-reported sexual activity variable in NSFG is more likely to capture sexually active women than the reproductive health care claims used for identifying sexually active women in the HEDIS measure because the HEDIS measure includes only women who used reproductive health care services.18 Our study has shown that many sexually active women did not have reproductive health services, and some women who had reproductive health services did not have a sex partner in the past year.
NSFG had a high response rate, collected sensitive data using careful methods with audio computer-assisted self-interviewing, and provided a nationally representative estimate of chlamydia testing coverage. Our study has several limitations. First, self-reported chlamydia testing and positivity are subject to recall bias and reporting errors, with possible under- or overestimation of the chlamydia testing rate and test positivity. Second, chlamydia testing or positivity could not be validated. Our estimate of 9.2% chlamydia positivity is higher than the 2002 NSFG estimate of 4.9% for all STD positivity and the 2009 Centers for Disease Control and Prevention surveillance estimate of 3.3% for chlamydiaal infection rate among all women aged 15 to 25 years.8,1 Further, our study could not identify the proportion of chlamydial infections that were due to screening or diagnostic testing. Finally, the NSFG has only limited geographic information; therefore, we could not estimate chlamydia testing rates by state or region.
In summary, fewer than half of sexually active women reported a chlamydia test, even if they also reported using reproductive health care services. These findings underscore the need for interventions to increase testing of young women and perhaps to develop empirically based algorithms to improve screening criteria to maximize yield under the current testing levels.
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