There have been no recent US population-based estimates of syphilis seroprevalence. We determined the prevalence of syphilis seroreactivity among a representative sample of the US population.Methods:
Sera from 18- to 49-year-old participants in the National Health and Nutrition Examination Surveys 2001–2004 were tested for syphilis IgG antibody using an enzyme immunoassay (EIA). Specimens with positive or indeterminate EIAs underwent rapid plasma reagin (RPR) testing; RPR titers ≥1:8 were considered positive. Specimens with RPR titers <1:8 underwent confirmatory testing with Treponema pallidum particle agglutination (TP-PA).Results:
Sera were available for 5767 participants. EIA testing was positive or indeterminate for 126, of which 10 had RPR titers ≥1:8. Of the remaining 116 specimens, 60 had positive TP-PA tests, including all 19 with RPR titers >1:1. Overall weighted syphilis seroprevalence was 0.71% (95% CI: 0.51–0.96). Prevalence was similar among males (0.76%) and females (0.67%) and increased with age, less education, and lower income (P <0.001 for each). Non-Hispanic blacks had the highest prevalence (4.3%), followed by Mexican-Americans (0.98%) and non-Hispanic whites (0.07%; P <0.001).Conclusions:
The prevalence of syphilis seroreactivity was low (0.71%) in the general US population of 18- to 49-year-olds. However, consistent with surveillance data, this nationally representative survey showed substantial disparities in syphilis by race/ethnicity.