A Population-Specific Optimized GeneXpert Pooling Algorithm for Chlamydia trachomatis and Neisseria gonorrhoeae To Reduce Cost of Molecular Sexually Transmitted Infection Screening in Resource-Limited Settings.

The sexually transmitted infections (STIs) chlamydia (CT) and gonorrhea (NG) are often asymptomatic in women and undetected by syndromic management, leading to complications such as pelvic inflammatory disease, infertility, and ectopic pregnancy. Molecular testing, such as the GeneXpert CT/NG assay, is highly sensitive, but cost restraints preclude implementation of these technologies in resource-limited settings. Pooled testing is one strategy to reduce the cost per sample, but the extent of savings depends on disease prevalence. The current study describes a pooling strategy based on identification of sociodemographic and laboratory factors associated with CT/NG prevalence in a high-risk cohort of Zambian female sex workers and single mothers conducted from 2016 to 2019. Factors associated with testing positive for CT/NG via logistic regression modeling included city, younger age, lower education, long-acting reversible contraception usage, Trichomonas vaginalis infection, bacterial vaginosis, and incident syphilis infection. Based on these factors, the study population was stratified into high-, intermediate-, and low-prevalence subgroups and tested accordingly-individually, pools of 3, or pools of 4, respectively. The cost per sample was reduced from $18 to as low as $9.43 in the low-prevalence subgroup. The checklist tool and pooling approach described can be used in a variety of treatment algorithms to lower the cost per sample and increase access to molecular STI screening. This is particularly valuable in resource-limited settings to detect and treat asymptomatic CT/NG infections missed by traditional syndromic management.