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Estimating Chlamydia Screening Rates by Using Reported Sexually Transmitted Disease Tests for Sexually Active Women Aged 16 to 25 Years in the United States

Tao, Guoyu PhD; Tian, Lin H. MD, MS; Peterman, Thomas A. MD, MS

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Sexually Transmitted Diseases: March 2007 - Volume 34 - Issue 3 - p 180-182
doi: 10.1097/01.olq.0000230437.79119.31
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AN ESTIMATED 3 MILLION NEW cases of Chlamydia trachomatis (CT) occur annually, making CT the most common bacterial sexually transmitted disease (STD) in the United States.1 Most infections in women are asymptomatic, but they may progress to serious sequelae such as pelvic inflammatory disease (PID), ectopic pregnancy, infertility, and chronic pelvic pain. Routine CT screening for sexually active women aged ≤25 years is recommended by several national organizations.2–7 In addition, Partnership for Prevention, a national nonprofit organization, ranks CT screening as one of the top 10 preventive services recommended for adolescents and adults in terms of disease burden prevented and cost-effectiveness.8

Despite these recommendations for annual CT screening, only a few studies have estimated the national population-based CT screening rates and the estimates varied widely.9–12 For example, one study estimated the CT screening rate was 60% for sexually active females aged 15 to 19 years in the U.S. general population in 2000.9 Another study, using the 1999–2001 data from the Health Plan Employer Data and Information Set (HEDIS) reported by commercial and Medicaid health insurance plans, estimated that CT screening rates of sexually active women aged 16 to 26 years were 26% for women enrolled in commercial plans and 38% for women enrolled in Medicaid plans in 2001.10 The wide estimates in those 2 studies may be because one study was based on reported cases and test positivity rates to project the number of tests performed for the U.S. general population and the other was based on claims data for commercially insured and Medicaid populations only.

To have a better estimate of the national CT screening rate, we conducted this study using data from a national survey. Our objective was to estimate CT screening rates using self-reported STD testing histories of sexually active women aged 16 to 25 years in the U.S. general population.



We analyzed data from the 2002 National Survey of Family Growth (NSFG). Details of the 2002 NSFG data have been published elsewhere.13 Briefly, the 2002 NSFG includes a nationally representative sample of 7,600 women and 4,900 men aged 15 to 44 years who were interviewed in person between March 2002 and March 2003. The survey was designed to provide national estimates of factors affecting pregnancy and birth rates, and it had an overall response rate of 80% for women and 78% for men. The survey data were generally collected by computer-assisted personal interviewing. However, the 2002 NSFG also contained a number of questions designed to provide a comprehensive description of respondents' substance use, STD/HIV risk behaviors, medical services for STDs, and sexual orientation. For better collection of that kind of sensitive and stigmatized information, the questions were asked by audio computer-assisted self-interviewing, in which the respondent entered the answers directly into the computer without the interviewer knowing the responses.

Sexual Activity, Sexually Transmitted Disease Tests, and Medical Services in the Preceding 12 Months

We focused on sexually active women aged 16 to 25 years. Sexual activity was based on the question in the 2002 NSFG: “Thinking about the past 12 months, that is, since (12 months earlier, 2001), how many male sex partners have you had? Please count every partner, even those you had sex with only once.”

STD tests were estimated by the following question: “In the past 12 months, that is, since (12 months earlier, 2001), have you been tested by a doctor or other medical care provider for a sexually transmitted disease like gonorrhea, chlamydia, herpes, or syphilis?” Because CT screening was not specified in the questionnaire, we used the reported STD testing rate to represent CT screening rate. In this way, the reported STD testing rate should be considered as the maximum CT screening rate. In addition, women in the 2002 NSFG were asked, “In the last 12 months, have you been told by a doctor or other medical care provider that you had chlamydia?” The positivity rate for CT in this study was then defined as the proportion of women who reported having been told that they had CT relative to the number of women who reported having had STD tests in the preceding 12 months.

Women were also asked many questions on reproductive health-related medical services, including questions about a method of birth control, a prescription for a birth control method, a checkup or medical test related to using a birth control method, counseling or information about getting sterilized, emergency contraception or the “morning-after pill,” counseling or information about emergency contraception, a pregnancy test, an abortion, a Pap smear, a pelvic examination, prenatal care, postpregnancy care, or counseling for, or having been tested or treated for an STD in the preceding 12 months. Women were classified as having had a Pap smear or pelvic examination if they reported they had received a Pap smear or pelvic examination from a physician or other medical provider in the preceding 12 months.

Women's Social–Demographic Characteristics

Data were analyzed according to the women's age, race/ethnicity, health insurance type, and place of residence. Age was classified into 3 groups: 16–18, 19–21, and 22–25 years. Race/ethnicity was categorized as Hispanic, non-Hispanic white, non-Hispanic black, and non-Hispanic other. Insurance type was classified as Medicaid or public program, private, and no health insurance. Residence was divided into metropolitan central city, metropolitan other, and nonmetropolitan areas.

Data Analyses

To account for the complex sampling design of the NSFG data, we used SUDAAN statistical software for analyzing survey data to generate the standard errors (SEs) for STD testing rates.14

Bivariate analysis and the chi-squared statistic were used to examine which variables were significantly related to the likelihood of having STD tests. Variables that were significantly associated with STD tests in bivariate analyses were included in a logistic regression model in which STD testing was the dependent variable. In all analyses, a statistically significant difference was defined as a 2-tailed probability of <0.05. The association between independent variables and the dependent variable was estimated using odds ratios and 95% confidence intervals in SUDAAN.


Of 2,563 women aged 16 to 25 years sampled in the United States, 75.3% (SE, 1.2%) were classified as sexual active. Of those sexually active women: 22.6% were 16 to 18 years old and 31.2% were 19 to 21 years old; 63.8% were non-Hispanic white, 15.3% were non-Hispanic black, and 15.5% were Hispanic; 60.9% had private insurance and 22.1% had Medicaid or other public coverage; 30.4% had more than one male sex partner; 73.0% had at least a Pap smear or pelvic examination; 83.2% had at least one reproductive health-related medical service; and 41.8% had at least one STD test in the preceding 12 months (Table 1). Of those women tested for STDs, 4.9% (SE, 0.9%) reported having been told that they had CT in the preceding 12 months. Positivity rates for CT were estimated to be 8.1% (SE, 2.2%) for women covered by Medicaid or other public program and 4.2% (SE, 1.1%) for women with private insurance.

Sexually Transmitted Disease Testing for Sexually Active Women Aged 16 to 25 Years in the Preceding 12 Months in the United States in 2002

Bivariate analyses showed that sexually active women aged 16 to 25 years were more likely to be tested for STDs if they were: non-Hispanic black (55.2%) versus non-Hispanic white (39.4%); enrolled in Medicaid or other public program (53.7%) versus private health plan (38.9%); had 2 or more sex partners (55.1%) versus one (36.0%); or had a Pap smear or pelvic examination (53.1%) versus no such service (11.4%) (Table 1). These differences were all statistically significant in the multivariate logistic regression analysis.

There was no significantly statistical association between STD testing and patients' age group or residence on bivariate analyses, so those variables were not included in multivariate analysis.


Even if all women tested for STDs were screened for CT, only approximately 42% of the sexually active women aged 16 to 25 years would have been screened for CT. The CT screening rate estimated in this study was much lower than the rate (60%) reported in one previous study in which estimates were based on reported cases and test positivity rates at family planning clinics.9 This study also showed that women were significantly more likely to receive STD tests if they were enrolled in Medicaid rather than private health insurance plans. This is consistent with another previous study.10 Women with Medicaid also had higher CT positivity rates than women with private insurance coverage in our study.

The 42% screening rate and 4.9% positivity rate suggests there is great need to improve screening. Several studies have shown that interventions can increase CT screening rates.15–19 For example, at one commercial managed care organization, adding a protocol to collect CT specimens with routine Pap smears increased screening rates from 61% to 83% in 24 months.15 Another study also showed that forming a quality-improvement team, selecting clinic-specific improvement measures, and feedback on screening performance increased screening by nearly 40% within 18 months in adolescent clinics.16 The findings that 73% had a Pap smear or a pelvic examination and only 53% of those had STD tests in the preceding 12 months suggest that screening rates would increase if CT tests were done whenever young women had Pap smears or pelvic examinations. However, the finding also showed that 16.8% of sexually active women had no reproductive health-related medical services in the preceding 12 months, suggesting that there is a need to improve access to reproductive health-related medical care for those women.

This study has several limitations. First, the NSFG collects participant-reported data, so recall and reporting errors may occur and the STD screening rate may be under- or overestimated in this study. One study has suggested that self-report, compared with medical record review, was a viable data collection method for STD diagnoses.20 Second, sexual activity defined in this study differed from that defined in the HEDIS measure. The different definition of sexual activity may result in misclassification of some women. One study showed that the HEDIS measure (based on claims data) underestimated the number of women who were eligible for CT screening compared with self-reported survey data.21 Third, the positivity rate was based on participants' self-report and the results could not be confirmed. However, the positivity rate (4.9%) was consistent with the CT prevalence (4.8%) at the national level for women.22 Finally, the NSFG data we used did not have state or region information. Therefore, we could not estimate STD screening rates by state or region.

In summary, even if all women who said they were tested for STDs were screened for CT, only 42% of sexually active women aged 16 to 25 years would have been screened for CT, although screening is recommended for all of these women. There is great room for improvement in screening sexually active women aged 16 to 25 years in the general U.S. population. CT screening rates could be significantly increased if CT tests were performed when women had Pap smears or pelvic examinations, because most sexually active women have routine Pap smears or pelvic examinations.


1. Cates W Jr. Estimates of the incidence and prevalence of sexually transmitted diseases in the United States. Sex Transm Dis 1999; 26(suppl):S2–S7.
2. Centers for Disease Control and Prevention. Sexually transmitted diseases treatment guidelines 2002. MMWR Morb Mortal Wkly Rep 2002; 51:1–78.
3. US Preventive Services Task Force. Screening for chlamydia infection: Recommendations and rationale. Am J Prev Med 2001; 20:90–94.
4. Committee on Adolescent Health Care. Health Care for Adolescents. Washington, DC: American College of Obstetricians and Gynecologists, 2003:69–79.
5. Guidelines for Adolescent Preventive Services (GAPS): Recommendations and Rationale. Chicago: American Medical Association, 1994.
6. American Academy of Pediatrics, Committee on Practice and Ambulatory Medicine. Recommendations for preventive pediatric health care (RE9939). Pediatrics 2000; 105.
7. Hollblad-Fadiman K, Goldman SM. American College of Preventive Medicine practice policy statement: Screening for Chlamydia trachomatis. Am J Prev Med 2003; 24:287–292.
8. Coffield AB, Maciosek MV, McGinnis JM, et al. Priorities among recommended clinical preventive services. Am J Prev Med 2001; 21:1–9.
9. Levine WC, Dicker LW, Devine O, Mosure D. Indirect estimation of chlamydia screening coverage using public health surveillance data. Am J Epidemiol 2004; 160:91–96.
10. Centers for Disease Control and Prevention Chlamydia screening among sexually active young female enrollees of health plans—United States, 1999–2001. MMWR Morb Mortal Wkly Rep 2004; 53:983–985.
11. St. Lawrence JS, Montano DE, Kasprzyk D, Phillips WR, Armstrong K, Leichliter JS. STD screening, testing, case reporting, and clinical and partner notification practices: A national survey of US physicians. Am J Public Health 2002; 92:1784–1788.
12. Mangione-Smith R, McGlynn EA, Hiatt L. Screening for chlamydia in adolescents and young women. Arch Pediatr Adolesc Med 2000; 154:1108–1113.
13. Groves RM, Benson G, Mosher WD, et al. Plan and operation of cycle 6 of the National Survey of Family Growth. National Center for Health Statistics. Vital Health Stat 2005; 1.
14. Shah BV, Barnwell BG, Bieler GS. SUDAAN User's Manual, release 7.0. Research Triangle Park, NC: Research Triangle Institute, 1996.
15. Burstein GR, Snyder MH, Conley D, et al. Chlamydia screening in a health plan before and after a national performance measure introduction. Obstet Gynecol 2005; 106:327–334.
16. Shafer MA, Tebb KP, Pantell RH, et al. Effect of a clinical practice improvement intervention on chlamydia screening among adolescent girls. JAMA 2002; 288:2846–2852.
17. Gonen JS. Confronting STDs: A challenge for managed care. Women Health Issues 1999; 9(suppl):S36–46.
18. Bull SS, Jones CA, Granberry-Owens D, et al. Acceptability and feasibility of urine screening for chlamydia and gonorrhea in community organizations: Perspectives from Denver and St. Louis. Am J Public Health 2002; 51:256–259.
19. Scholes D, Stergachis A, Heidrich FE, et al. Prevention of pelvic inflammatory disease by screening for cervical chlamydial infection. N Engl J Med 1996; 334:1362–1366.
20. Niccolai LM, Kershaw TS, Lewis JB, Cicchetti DV, Ethier KA, Ickovics JR. Data collection for sexually transmitted disease diagnoses: A comparison of self-report, medical record reviews, and state health department reports. Ann Epidemiol 2005; 15:236–242.
21. Tao G, Walsh CM, Anderson LA, Irwin KL. Understanding sexual activity defined in the HEDIS measure of screening young women for Chlamydia trachomatis. J Quality Improvement 2002; 28:435–440.
22. Miller WC, Ford CA, Handcock MS, et al. Prevalence of chlamydial and gonococcal infections among young adults in the United States. JAMA 2004; 291:2229–2236.
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