Derivation and Internal Validation of a Risk Score for Predicting Chlamydia trachomatis Infection in Kenyan Women Planning Conception

Abstract

Background: Availability of laboratory confirmation of sexually transmitted infections is increasing in low-and middle-income countries, but costs continue to limit their access. Chlamydia trachomatis (CT) is a sexually transmitted infection of significant clinical importance, particularly among women. This study aimed to develop a risk score to identify women with a higher likelihood of CT infection, who could then be prioritized for laboratory testing, in a population of Kenyan women planning pregnancies.Methods: Women with fertility intentions were included in this cross-sectional analysis. Logistic regression was used to estimate odds ratios for the association between demographic, medical, reproductive, and behavioral characteristics and the prevalence of CT infection. A risk score was developed and validated internally based on the regression coefficients in the final multivariable model. Results:The prevalence of CT was 7.4% (51 of 691). A risk score for predicting CT infection, with scores 0 to 6, was derived from participants' age, alcohol use, and presence of bacterial vaginosis. The prediction model yielded an area under the receiver operating curve of 0.78 (95% confidene interval [Cl], 0.72-0.84). A cutoff of ≤2 versus >2 identified 31.8% of women as higher risk with moderate sensitivity (70.6%; 95% Cl, 56.2-71.3) and specificity (71.3%; 95% Cl, 67.7-74.5). The bootstrap-corrected area under the receiver operating curve was 0.77 (95% Cl, 0.72-0.83). Conclusions:In similar populations of women planning pregnancies, this type of risk score could be useful for prioritizing women for laboratory testing and would capture most women with CT infections while performing more costly testing in less than half of the population.