Appraising the HIV Prevention Cascade methodology to improve HIV prevention targets: Lessons learned from a general population pilot study in east Zimbabwe.

Introduction: Multiple HIV Prevention Cascades (HPC) formulations have been proposed to assist advocacy, monitoring of progress of HIV prevention implementation and research to identify ways to increase use of HIV prevention methods. Schaefer and colleagues proposed a unifying formulation suitable for widespread use across different populations which could be used for routine monitoring or advocacy. Robust methods for defining and interpreting this HPC formulation using real world data is required. Methods: Data collected as part of the Manicaland Pilot HIV Prevention Cascades Study, east Zimbabwe, in 2018-19, was used to validate the HPC framework for PrEP, VMMC, male condom and combination prevention method use. Validation measures included feasibility of populating the HPC, contrasting simple vs complex measures of the HPC (using 2-sample proportion test), and testing ability of main bars to predict prevention use and testing whether sub-bars explained why people were lost from the HPC using logistic regression. Results: It was possible to populate the HPC for both individual and combined prevention methods using pilot survey data. Most steps were associated with prevention method usage outcomes, except for VMMC. There were significant overlaps between individuals reporting positive responses for the main bar and those citing barriers to motivation. To refine the HPC's access bar definition, it is suggested to also consider individuals who report access barriers. While the HPC framework identifies barriers to individual prevention methods, challenges arise in identifying those for combined prevention. Discussion: Our study successfully utilised questionnaires from the Manicaland HPC pilot survey to measure the HPC for individual and combined prevention methods. This demonstrates the feasibility of populating this framework using general population survey data and designated questionnaire modules. We propose a final formulation of the HPC, questionnaire modules and methods to create it. With proper evaluation and promotion, the HPC can enhance prevention services, aiding in the crucial reduction of HIV incidence.