RESUMO
BACKGROUND: Intervention effectiveness in a randomized controlled trial is attributed to intervention fidelity. Measuring fidelity has increasing significance to intervention research and validity. The purpose of this article is to describe a systematic assessment of intervention fidelity for VITAL Start (Video intervention to Inspire Treatment Adherence for Life)-a 27-minute video-based intervention designed to improve antiretroviral therapy adherence among pregnant and breastfeeding women. METHOD: Research Assistants (RAs) delivered VITAL Start to participants after enrolment. The VITAL Start intervention had three components: a pre-video orientation, video viewing, and post-video counseling. Fidelity assessments using checklists comprised self (RA assessment) and observer (Research Officers, also known as ROs) assessment. Four fidelity domains (adherence, dose, quality of delivery, and participant responsiveness) were evaluated. Score scale ranges were 0 to 29 adherence, 0 to 3 dose, 0 to 48 quality of delivery and 0 to 8 participant responsiveness. Fidelity scores were calculated. Descriptive statistics summarizing the scores were performed. RESULTS: In total, eight RAs delivered 379 VITAL Start sessions to 379 participants. Four ROs observed and assessed 43 (11%) intervention sessions. The mean scores were 28 (SD = 1.3) for adherence, 3 (SD = 0) for dose, 40 (SD = 8.6) for quality of delivery, and 10.4 (SD = 1.3) for participant responsiveness. CONCLUSION: Overall, the RAs successfully delivered the VITAL Start intervention with high fidelity. Intervention fidelity monitoring should be an important element of randomized control trial design of specific interventions to ensure having reliable study results.