Objectives In settings where laboratory capacity is limited, the WHO recommends presumptive treatment for Neisseria gonorrhoeae (NG) and Chlamydia trachomatis (CT) in asymptomatic men who have sex with men (MSM) at high risk for these infections. However, little is known about how best to target this intervention. We aimed to identify correlates of anorectal NG/CT infection in Kenyan MSM with and without anorectal symptoms and evaluate the performance of an empirical, model-based risk score to identify cases in asymptomatic men.
Methods Anorectal NG/CT infections were diagnosed by the Abbott RealTime NG/CT nucleic acid amplification testamong 698 MSM at enrolment into the Anza Mapema study. Multivariable logistic regression was used to identify correlates of anorectal NG/CT infection in men with and without anorectal symptoms. Using coefficients from the final multivariable model for asymptomatic men, we calculated a risk score for each participant. Risk score performance was determined by calculating the sensitivity, specificity and number needed to treat (NNT) to identify one NG/CT infection.
Results Overall anorectal NG/CT infection prevalence was 5.2% (n=36), of which 58.3% (n=21) were asymptomatic. Factors associated with anorectal NG/CT infection in asymptomatic men were aged 18–24 years (aOR=7.6; 95% CI: 1.7 to 33.2), HIV positive serostatus (aOR=6.9; 95% CI: 2.2 to 21.6) and unprotected anal sex in the past 3 months (aOR=3.8; 95% CI: 1.2 to 11.9). Sensitivity and specificity were optimal (81.0% and 66.1%, respectively) at a model-derived risk score cut-point ≥3, and the NNT was 12.
Conclusions A model-derived risk score based on correlates of anorectal NG/CT infection in asymptomatic participants would be sensitive and efficient (i.e, low NNT) for targeting presumptive treatment. If validated in other settings, this risk score could improve on the WHO algorithm and help reduce the burden of asymptomatic anorectal NG/CT infections among MSM in settings where diagnostic testing is not available.
- Neisseria gonorrhoea
- Chlamydia trachomatis
- anogenital conditions
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Handling editor Khalil G Ghanem
Contributors LASQ and SMG designed the study. FO and DO oversaw implementation of STI testing. EO and CK assisted with data management and cleaning. LASQ and SMG conducted the analyses. RCB, GD and BON contributed to study implementation and oversight. All authors contributed to and approved the final manuscript.
Funding The Anza Mapema Study was supported through funding provided by the Centers for Disease Control and Prevention (U01GH000762) and by Evidence for HIV Prevention in Southern Africa (MM/EHPSA/NRHS/0515008). LASQ was supported through funding by the Centers for Disease Control and Prevention (1U 62 PS 004584-01) and the University of Washington Thomas Francis, Jr. Global Health Fellowship.
Competing interests None declared.
Patient consent Not required.
Ethics approval The Anza Mapema Study obtained ethics approval from the Maseno University Ethics Review Committee (Reference MSU/DRPC/MUERC/00104/14), the University of Washington institutional review board (Protocol 48148) and the University of Illinois-Chicago institutional review board (IRB Protocol 2014-0778). All participants gave informed consent before taking part in the study.
Provenance and peer review Not commissioned; externally peer reviewed.
Data sharing statement Researchers requesting access to data/resources will be asked to submit a request in writing describing their qualifications including their certification by their local IRB, analytic plans and other uses of the data/resources, and plans to secure the confidentiality and safety of the data. They will be required to agree in writing that they will not share the data with others, will use it only for the research purpose(s) delineated and will return or destroy the data on completion. In order to maintain protection of our participants’ privacy, no directly identifying information will be shared with outside investigators. Given the sensitive nature of the data we are collecting, including HIV diagnosis and same-sex behaviors, no public access file is available.
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