Seroprevalence of Chlamydia trachomatis Among Female Adults in the United States: The National Health and Nutrition Examination Surveys

Abstract

Background: Chlamydia trachomatis is the most common nationally notifiable sexually transmitted infection in the United States; however, the seroprevalence of C. trachomatis infection is unknown.

Methods: This cross-sectional study was conducted among 1725 females aged 18 to 39 years who provided serum and urine samples in the 2013 through 2016 National Health and Nutrition Examination Surveys. Presence of anti-C. trachomatis Pgp3 immunoglobulin G (IgG) was determined using both an enzyme-linked immunosorbent assay (ELISA) and multiplex bead array (MBA). Weighted seroprevalence estimates were calculated. Correlates of seroprevalence were examined by multivariable Poisson regression.

Results: In 2013 through 2016, overall seroprevalence of C. trachomatis Pgp3 IgG was 30.0% (95% confidence interval [CI], 25.5-35.0) as measured by ELISA and 29.4% (95% CI, 25.8-33.0) as measured by the MBA assay. Overall agreement between tests was 87.1% (1503/1725). There was a high positive agreement by the MBA assay with current detection of chlamydia in urine (86% [36/42]), a past-year diagnosis of chlamydia (81.8% [27/33]), and a history of treatment for pelvic inflammatory disease (60.7% [37/61]). Seroprevalence of C. trachomatis Pgp3 IgG, as measured by MBA, was significantly higher among non-Hispanic Blacks (68.0%; adjusted prevalence ratio (aPR) = 2.7 [95% CI, 2.3-3.3]), Mexican Americans (30.9%; aPR = 1.5 [95% CI, 1.2-1.9]), and other Hispanics (35.0%; aPR = 1.9 [95% CI, 1.4-2.5]) compared with non-Hispanic Whites (21.4%). A higher lifetime number of sexual partners and a younger age at sexual debut was also associated with higher seroprevalence.

Conclusion: Both the ELISA and MBA serologic assays revealed a high prevalence of antibodies to C. trachomatis Pgp3 in young adult females in the US household population. There were major racial/ethnic disparities in exposure to C. trachomatis, with increased vulnerability among non-Hispanic Black females.

Keywords: Chlamydia trachomatis; National Health and Nutrition Examination Surveys (NHANES); Pgp3 antibody; enzyme-linked immunosorbent assay (ELISA); multiplex bead array (MBA); seroprevalence.

Figure 1.

Chlamydia trachomatis seroprevalence among US females aged 18 to 39 years. A, Concordance and discordance of 2 anti-C. trachomatis Pgp3 IgG assays among females age 18–39 (n = 697). MBA positivity is represented in yellow, ELISA positivity represented in blue and concordance of MBA and ELISA in green. B, Anti-C. trachomatis Pgp3 IgG positivity among females with current chlamydia detection by urine NAAT test (n = 42) and without chlamydia detection (n = 1683). C, Anti-C. trachomatis Pgp3 IgG positivity among females diagnosed with chlamydia in the past 12 months (n = 33) and those not diagnosed (n = 1391). D, anti-C. trachomatis Pgp3 IgG positivity among females ever treated for PID or pelvic infection (n = 61) and those not diagnosed (n = 1471). Note: Data are unweighted. 95% confidence intervals are exact binomial confidence intervals. Definitions of positivity: ELISA, positive on the anti-pgp3 ELISA; MBA, positive on the anti-pgp3 MBA; Both, positive on both an anti-pgp3 MBA and ELISA; Either, positive on either the anti-pgp3 MBA and ELISA. Abbreviations: IgG, immunoglobin G; ELISA, enzyme-linked immunosorbent assay; MBA, multiplex bead format assay; NAAT, nucleic acid amplification test; Pgp3, plasmid gene product 3; PID, pelvic inflammatory disease.

Figure 2.

Seroprevalence of Chlamydia trachomatis (C. trachomatis) and herpes simplex virus 2 by age and race among US females age 18 to 39 years. Note: C. trachomatis prevalence as determined by a multiplex bead array (MBA). Abbreviations: HSV-2, herpes simplex virus 2; US, United States.