Empirical progression criteria thresholds for feasibility outcomes in HIV clinical trials: a methodological study

Pilot and feasibility trials use predetermined thresholds for feasibility outcomes to decide if a larger trial is feasible. These thresholds may be derived from the literature, observational data, or clinical experience. The aim of this study was to determine empirical estimates for feasibility outcomes to inform future HIV pilot randomized trials.

We conducted a methodological study of HIV clinical trials indexed in the past 5 years (2017-2021) in the PubMed database. We included trials of people living with HIV individually randomized to any type of intervention and excluded pilot trials and cluster randomized trials. Screening and data extraction were conducted in duplicate. We computed estimates for recruitment, randomization, non-compliance, lost to follow-up, discontinuation, and the proportion analyzed using a random effects meta-analysis of proportions and reported these estimates according to the following subgroups: use of medication, intervention type, trial design, income level, WHO region, participant type, comorbidities, and source of funding. We report estimates with 95% confidence intervals.

We identified 2122 studies in our search, of which 701 full texts were deemed relevant, but only 394 met our inclusion criteria. We found the following estimates: recruitment (64.1%; 95% CI 57.7 to 70.3; 156 trials); randomization (97.1%; 95% CI 95.8 to 98.3; 187 trials); non-compliance (3.8%; 95% CI 2.8 to 4.9; 216 trials); lost to follow-up (5.8%; 95% CI 4.9 to 6.8; 251 trials); discontinuation (6.5%; 95% CI 5.5 to 7.5; 215 trials); analyzed (94.2%; 95% CI 92.9 to 95.3; 367 trials). There were differences in estimates across most subgroups.

These estimates may be used to inform the design of HIV pilot randomized trials with careful consideration of variations due to some of the subgroups investigated.