P3.333 Chlamydia Trachomatis IgG Seroprevalence in the General Population of the Netherlands in 1996 and 2007

Background Chlamydia trachomatis (Ct) reporting rates from sexually transmitted infection (STI) clinics and general practitioners have shown a rising trend in the Netherlands. It is unknown to what extent this reflects increased Ct transmission or improved case-finding. To achieve more insight into the dynamics of the Ct epidemic, we explored the Ct IgG seroprevalence (marker of past Ct infection) in the general population of the Netherlands in 1996 and 2007. Methods From two independent population-based studies in 1996 and 2007, serum samples were drawn, from 650 men and 1,000 women per study. Participants completed a questionnaire covering demographic information and sexual risk factors. Serum antibodies were analysed using Medac CtIgG ELISA test. Multivariate logistic regression analyses explored changes in, and determinants of Ct IgG seroprevalence. Results The Ct IgG seroprevalence was higher in women than in men in 1996 (11.3% vs 5.2%), but this difference had diminished in 2007 (8.4% vs 6.9%). Among women aged 25–40 years, the seroprevalence was significantly lower (OR 0.6 [0.4–0.8]) in 2007 than in 1996, whereas the seroprevalence among women aged 15–24 years and men in both age groups was slightly higher in 2007, though not significantly. Determinants of seropositivity were female gender (OR 1.7 [1.3–2.0]), known history of Ct infection (OR: 3.4 [1.7–6.8]), 25–40 years old (OR 1.6 [1.1–2.4]), non-western ethnicity (OR: 1.8 [1.1–3.2]) and ≥ 2 recent sexual partners (OR: 2.2 [1.4–3.7]). Conclusion Ct IgG seropositivity was associated with known STI risk factors. Our results suggest that the proportion of individuals in the population who have had a Ct infection did not increase between 1996 and 2007. The decrease in seroprevalence among women aged 25–40 years between 1996 and 2007 may indicate changes in Ct transmission due to a more pro-active ‘test and treat’ policy.