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Background: Among reproductive-age women, chlamydia, gonorrhea and Trichomonas vaginalis are the most common non-viral STDs. National guidelines recommend screening all sexually active women <25 years old for chlamydia. Because there are several bi-valent diagnostic assays for chlamydia and gonorrhea, many young women are tested for both infections.
Objectives: To examine whether, given the overall prevalence of trichomonas, a tri-valent assay for all three infections would be a useful diagnostic tool.
Methods: Women aged 15-39 years who participated in National Health and Examination Surveys (NHANES) cycles 2001 – 2004 provided specimens for STD testing. Nucleic acid amplification assays were used to test for chlamydia, gonorrhea and trichomonas. The weighted prevalence for each infection was calculated by age and race/ethnicity.
Results: Among women 15-19 years (the peak age for chlamydia and gonorrhea) the prevalence for chlamydia, gonorrhea and trichomonas was 4.7%, 1.3% and 2.1%, respectively. Among those 30-39 years (the peak age for trichomonas) the prevalence was: 1.6%, 0.3% and 4.1% respectively. The prevalence of trichomonas among 15-19 year olds vs. 30-39 year olds by race/ethnicity was as follows: white, 0.8% vs. 1.5%; Hispanic, 1.0% vs. 5.9%; and black, 9.8% vs. 16.7%.
Conclusions: While the age-prevalence trends were similar for chlamydia and gonorrhea with women 15-19 years having the highest prevalence, the trend for trichomonas was the inverse with women 30-39 years having the highest prevalence.
Implications for Programs, Policy, and/or Research: A tri-valent assay targeting younger women, the target for population-based chlamydia screening, would miss most trichomonas infections. Given the markedly different age distribution of these infections in the general population, a tri-valent assay could result in over-screening for chlamydia and gonorrhea in the populations at greatest risk for trichomonas, women 30-39 years. Because of the low prevalence of each infection in some sub-populations, the positive predictive value of results for a given infection might be substantially compromised with a tri-valent assay.