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Table 2 Methods to reduce contamination during all phases of the proposed research and ensure intervention fidelity

From: The Video intervention to Inspire Treatment Adherence for Life (VITAL Start): protocol for a multisite randomized controlled trial of a brief video-based intervention to improve antiretroviral adherence and retention among HIV-infected pregnant women in Malawi

Trial design and pre-implementation

▪ Increased sample size to account for potential contamination (up to 15%)

▪ Focus group discussions and literature reviews have explored types, extent of, and measures to reduce possible contamination sources. Overall risk of contamination deemed to be very small

▪ Focus group discussions identified video recall items to measure contamination

▪ Trial staff and trial clinic training emphasizes the implications of contamination, how to avoid it, how to address questions using non-biased explanations, and the need to ensure VITAL Start and SOC are delivered in separate places


▪ VITAL Start and SOC occur in separate locations, and intervention is delivered by trained RAs

▪ Participants will be escorted between counseling and survey locations

Level and extent of patient-reported contamination is measured at follow-up visits

▪ Video is on password-protected tablet that is stored at the health facility and not available through other channels

▪ Information packs with VITAL Start materials are clearly labeled and stored separately from SOC materials

▪ Any accidental contamination by trial or health facility staff will be recorded on Unanticipated Problems Forms that are reviewed monthly at site-level meetings and supervisions

▪ Site Research Supervisor to confirm trial participants only receive assigned intervention

▪ Rationale and techniques for reducing contamination discussed at monthly site meetings with health facility and trial staff

▪ Information regarding participant’s trial arm allocation is kept in a locked drawer that can only be accessed by RA

▪ Contamination is measured quarterly as a component of checklist to measure the degree of fidelity [63]

Strategies to ensure treatment fidelity

▪ Fidelity checklists completed by RA (self-administered) and observer. Key issues discussed at quarterly staff meetings

▪ Intervention sessions audio recorded, and 10% reviewed centrally

▪ Electronic time-stamps of session start and end time and bi-monthly supervisions by trial coordinator

▪ Unannounced trial coordinator visits

▪ Plans for implementation setbacks which include two providers (RAs) per site, back-up tablets, paper forms, power banks, and back-up physical space for intervention implementation


▪ If contamination occurs, we will perform contamination-adjusted intention-to-treat analysis [64]

▪ The degree, nature, and effects of contamination will be included in final manuscripts