Introduction The Netherlands Chlamydia Cohort Study (NECCST) follows a cohort of women of reproductive age for ≥10 years to investigate Chlamydia trachomatis (CT) related risk (factors) for late complications including the role of host genetic biomarkers. This cohort builds on a prior large-scale Chlamydia Screening Implementation (CSI, 2008–2011). Here outcomes from the first NECCST collection round are described.
Methods In 2015–16 CSI women were invited to participate in NECCST. Data on CT-infections, pregnancies and the late complications Pelvic Inflammatory Disease (PID), ectopic pregnancy (EP) and tubal infertility (TI) were collected by questionnaires. CT Immunoglobulin G (IgG) was measured in self-collected blood samples. A positive CT history was defined as ≥1 positive outcome, either a positive CSI CT Polymerase Chain Reaction (PCR) result, a self-reported CT-infection or CT IgG presence. Risks were compared between women with/without a positive CT-history in NECCST-data combined with CSI-data.
Results Among the 5704 women enrolled, CT IgG prevalence was 14.5%. Of women with self-reported CT-infection or who had been CSI-PCR positive, 38.1% was CT-IgG positive. Of women without a self-reported CT-infection and who had been CSI-PCR negative, 7.0% was CT-IgG positive. Overall 29.2% (n=1,665) had a positive CT-history. Women with a positive CT-history reported less planned pregnancies compared to women with a negative CT-history (19.5% vs 27.4%, p<0.001). In contrast, unplanned pregnancies were more common among women with a positive CT-history (24.7% vs. 12.4%, p<0.001). Women with a positive CT-history had a significantly higher risk of PID and TI compared to women with a negative CT-history: 5.0% vs. 2.0% (p<0.001) and 1.1% vs. 0.3% (p<0.001), respectively.
Conclusion Intermediate outcomes of NECCST after 4–7 years follow-up from CSI suggest a higher risk for PID and TI in women with a positive CT-history. NECCST is expected to yield valuable results for identification of risk factors for CT-complications which might enable targeted preventive methods.