CHLAMYDIA TRACHOMATIS IS THE most commonly reported bacterial sexually transmitted disease (STD) in the United States. In women, chlamydial infections cause substantial morbidity, especially among those 15–24 years of age.1 Genital chlamydial infection in women may cause pelvic inflammatory disease, tubal infertility, ectopic pregnancy, and chronic pelvic pain2,3 and additionally may increase the risk for human immunodeficiency virus (HIV) infection4,5 and cervical carcinoma.6,7 Two-thirds of women with chlamydial infection in the cervix have no signs or symptoms of the infection.8 Because of the asymptomatic nature of the disease, screening and treatment programs for chlamydial infection constitute an important component of the prevention effort to reduce the disease burden.
The National Job Training Program (NJTP) is an occupational training program for socioeconomically disadvantaged individuals aged 16–24 years old (i.e., high school dropouts, those in need of additional education, vocational training, or assistance to hold meaningful employment). During the training, most participants live in dormitories. At entrance into the training program, participants underwent physical examinations, including a chlamydia screening test. Those who were infected with chlamydia at the initial tests were retested at 1–2 months after completing treatment.
Recurrent infection after treatment may be due to reinfection and/or treatment failure9 (persistent infection) and occurs in approximately 10–15% of women treated for chlamydial infection and retested about 3 months after treatment.10 This recurrent infection serves as a reservoir of infection and may play an important part in undermining the success of the screening programs. In addition, recurrent chlamydial infection increases the likelihood for pelvic inflammatory disease and ectopic pregnancy.11,12 Thus, evaluation of factors associated with recurrent infection is important for effective implementation of retesting and retreatment programs. In this analysis, we evaluated factors associated with returning for retesting and compared risk factors for initial versus recurrent chlamydial infection in socioeconomically disadvantaged women entering the National Job Training Program from 1998 through 2005.
All women aged 16–24 years who were enrolled and screened at the training program from January 1998 through December 2005 were included in this analysis. Most women received pelvic examinations within 14 days of enrollment. At most program centers, cervical specimens were obtained during this examination. These cervical specimens were sent to a contract laboratory for the detection of chlamydial infection by a nonnucleic acid amplification test (GenProbe PACE 2, San Diego, CA). Starting in 2000, a small proportion of women was tested by a nucleic acid amplification test (NAAT) (BDProbeTec ET, Becton-Dickinson, Sparks, MD) to detect genital chlamydial infection using urine specimens. Women who were positive at the initial test were asked to return for retesting 1–2 months after completing treatment (mostly with a single dose of azithromycin). In addition to laboratory test type, year of test, and results, information was collected on individuals’ demographic characteristics (age, race/ethnicity, and state of residence). No incentives or reminders to return were provided, but all medical services and treatment were free. Additional information on the National Job Training Program can be found elsewhere.13
We computed chlamydia prevalence at initial and subsequent testing (1–2 months after completing treatment). In the analysis, we categorized sociodemographic variables as follows: age groups (16–19, 20–24 years), race/ethnicity (white, black, Hispanic, American Indian/Alaska Native, and Asian/Pacific Islander), geographic region of residence (Bureau of the Census regions—Northeast, South, Midwest, and West), chlamydia test type, and years of the test (1998–2000 and 2001–2005). We used the chi-square statistic to test for differences among proportions and logistic regression to estimate adjusted odds ratios (OR) and their 95% confidence intervals (CI) at initial testing and at retesting. Our analyses were conducted using two separate and unlinked databases, one containing information on women who were tested for chlamydia at program entrance and the other, a subset of the first, containing information on women who initially tested positive for chlamydia and were retested. We excluded women with missing values for race/ethnicity or residence from the multivariate analysis for the initial testing (there were no missing values for race/ethnicity or residence at the retesting).
We excluded 10,050 (8%) women from the analysis due to missing information on race/ethnicity and 12,555 (10%) due to missing information on state of residence. Of the 126,894 women included in the analysis13,550 (10.7%) had chlamydial infections (Table 1). A total of 5,892 (43.5%) infected women underwent retesting for chlamydial infections 1–2 months after completing treatment. The distribution of infected women who underwent retesting was different from the distribution of infected women who did not undergo retesting by age group, race/ethnicity, region, type of test, and year of test (data not shown). At the initial visit 10.2% of women were tested by the urine based BDProbeTec test compared with 25.6% at retesting (data not shown). At retesting, the percentage of women tested by the urine based BDProbeTEC was highest for whites (46.5%), for those residing in the Northeast (37.3%), and for those tested during the years 2001–2005 (40.3%) (data not shown). In addition, among initially infected women those with lower risk were likely to return. Younger age women (16–19 years), blacks and Hispanics, those who resided in the South and Midwest, and those tested in 1998–2000 were less likely to be retested (Table 1).
Among those who were initially positive and retested 332 (5.6%) were positive again (Table 2). The initial chlamydia prevalence varied by age group, race/ethnicity, region of residence, type of test, and year of test. This pattern did not change after adjustment by the logistic regression analysis (Table 2). The factors associated with recurrent infection, although not statistically associated, were similar to those associated with the initial infection, highest in the younger age group, highest in blacks, highest in the South, lowest in the West, and highest in those tested by the urine based BDProbeTec. The pattern of recurrent infection did not change after adjustment in the logistic regression analysis, but the odds ratios were consistently smaller than for those factors associated with infection at the initial test and not statistically significant (Table 2).
This analysis is the first large-scale evaluation of recurrent chlamydial infection (due to reinfection and/or treatment failure) among young women from a socioeconomically disadvantaged population in a nonclinical setting (chlamydia test results were available for 86% of training participants).13 Previous reports on recurrent chlamydial infection (due to reinfection and/or treatment failure) have been conducted mostly among patients in clinical settings with smaller numbers of women.10,14,15 Our finding of recurrent infection in 5.6% of women is comparable with findings from these populations. Among female patients attending reproductive health, STD, and adolescent clinics in 5 cities in the United States, 6.3% had recurrent infection about 1 month after treatment.10 Another study found the same recurrent infection rate (6.3%) among female patients attending family planning, adolescent, STD, primary care clinics or emergency rooms about 1 month after treatment.14 A recent study that followed adolescent and young women for 48 months found that recurrent infection after initial infection increases with time until retesting.16 Among female patients who received a diagnosis of chlamydial infection in King county, WA from September 1998 to March 2003, 12.3% had recurrent chlamydial infection about 3 months after treatment.15 Peterman et al. also reported a 10.7% recurrent chlamydial infection rate among female patients attending 3 public STD clinics approximately 3 months after treatment.17
At retesting, the characteristics associated with chlamydial infection were similar to those at the initial test, but the ORs were smaller and not statistically significant. The smaller ORs at the retesting suggest that no factors dramatically contributed to the recurrent infection. Our findings at the initial test and at retesting may be somewhat different because retesting was conducted only in those who initially tested positive for chlamydia. Among initially infected women, those with lower risk were more likely to return, thus there may have been less variability in risk.
When compared with women attending family planning clinics and in the general population18,19 our analysis found a high prevalence of chlamydia among young women entering NJTP. Our analysis also found that age and race/ethnicity were not associated with recurrent chlamydial infection. Several studies have reported similar findings.10,17,20,21 Whittington et al. found that age was not associated with chlamydial infection at retesting but was associated with failure to complete treatment or resuming sexual activities.10 Another study also found that risk of subsequent chlamydial infection was independent of age.20 Others found that young age (<25 years) compared with older age (≥30 years) was associated with an increased risk of recurrent infection.15,22 However, we might not have detected an association with age because we analyzed recurrent infection in young women within a narrow range (16–24 years). When several STDs (chlamydia, gonorrhea, and/or trichomonas), were evaluated among female patients, black race was associated with an increased risk of recurrent STDs.17,21 If 2–3% of recurrent infection is due to treatment failure,23 approximately 3% of the recurrent infections 1–2 months after completing treatment might be due to reinfection. This high proportion of treatment failure might have reduced the association of recurrent infection with age and race/ethnicity.
We could not formally evaluate the impact of the laboratory test type (the urine based BDProbeTEC compared with the GenProbe test requiring an endocervical specimen) at the initial visit on the retesting rate at return visit because we did not have information on which individual women, initially testing positive for chlamydia, returned for a follow-up test. When compared with the women initially tested the women who did undergo retesting were more likely to be tested with a urine-based assay but we cannot say whether having a urine based test contributed to their being retested
CDC recommends that women should be retested for chlamydial infection approximately 3 months after completing treatment24 to detect reinfection as well as treatment failure. In this analysis, we found a high rate of infection (5.6%) at an even shorter retesting duration than that recommended by CDC. High recurrent infection may be due to reinfection and/or treatment failure. Reinfection from sexual partners might be reduced by counseling the participant to use barrier contraception consistently for any sexual encounters.25,26 In addition, treatment of sexual partners through expedited or standard referral mechanism might also reduce the risk of reinfections.15 Unfortunately, no information on counseling and partner notification was available for this population.
There are several limitations to this analysis. First, the sensitivity of the GenProbe chlamydia test is significantly lower than the sensitivity of the BDProbeTEC test.27,28 This difference may have affected the chlamydia prevalence results at both initial testing and retesting. Because the number of women retested by the BDProbeTEC was not sufficiently large, we were not able to evaluate adequately the chlamydia prevalence for age, race/ethnicity, region, and year of test detected by the BDProbeTEC only. Second, chlamydia retesting was performed within a short duration (1–2 months) after treatment. In this situation, amplification and nonamplification of nucleic acid might detect dead chlamydia trachomatis and give false positive results. False positive results probably did not significantly affect the findings of this analysis for several reasons: first, most of the dead organisms were probably washed out after 3 weeks of treatment24; second, most of the retesting used a non-NAAT (GenProbe) which is less sensitive than the NAAT (BDProbeTEC). Third, the absolute number of retested women was much smaller than the number initially tested; complicating comparisons of the ORs, but ORs at retesting were consistently smaller and in the same direction as ORs at initial testing. Fourth, lower risk women were more likely to be retested; therefore might introduce bias toward underestimation of the true recurrence rate. Last, the proportion of initially infected women who failed to be retested was high and the sociodemographic characteristics of those who did and did not undergo retesting were different.
In summary, we found a high prevalence of chlamydia at initial and retesting among socioeconomically disadvantaged women entering the NJTP from 1998 to 2005. At retesting, the chlamydia prevalence did not vary substantially by sociodemographic characteristics. These findings indicate that the retesting program should be continued and more women should be retested. In addition, counseling on safe sex practices as well as partner treatment should be implemented vigorously for those with chlamydial infection. Because this program serves a high-risk population that lacks access to health care services after graduation, chlamydia screening and retesting at the training program play an important part in the prevention of chlamydia and its sequelae.
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