Predicting Sexually Transmitted Infections Among HIV+ Adolescents and Young Adults: A Novel Risk Score to Augment Syndromic Management in Eswatini.

BACKGROUND Despite poor predictive power, syndromic screening is standard of care for diagnosing sexually transmitted infections (STIs) in low-resource, high HIV-burden settings. Predictive models may augment syndromic screening when diagnostic testing is not universally available for screening high risk patient populations such as adolescents and young adults living with HIV. SETTING 415 adolescents and young adults living with HIV, age 15 to 24 years, participated from three clinical sites in Eswatini, provided urine, sexual and medical history, and completed physical examination. METHODS STI cases were defined by a positive Xpert result for Chlamydia trachomatis, Neisseria gonorrhea, or Trichomonas vaginalis. Features predictive of an STI were selected through Least Absolute Shrinkage and Selection Operator (LASSO) with 5-fold cross validation. Various model strategies were compared with parametric AUC estimation and inferences were made with bootstrapped standard errors. RESULTS Syndromic screening poorly predicted STIs (AUC 0.640 (95% Confidence Interval (95%CI): 0.577, 0.703). A model considering five predictors (age group, sex, any sexual activity, not always using condoms (either self or partner), a partner who was 25 years or older, and horizontal or unknown mode of HIV acquisition) predicted STIs better than syndromic screening (AUC: 0.829 (95% CI: 0.774, 0.885)) and was improved when the risk score was supplemented with leukocyte esterase (LE) testing (AUC: 0.883 (95% CI: 0.806, 0.961)). CONCLUSION This simple predictive model, with or without leukocyte esterase testing, could improve STI diagnosis in HIV-positive adolescents and young adults in high burden settings through complementary use with syndromic screening and to guide patient selection for molecular STI diagnostic tests.