Factors associated with trial recruitment and retention of people with osteoarthritis: analysis of 215 randomised controlled trials from 2013-2021

AIMS: To identify recruitment and retention rate in randomised controlled trials (RCTs) recruiting people with hip or knee OA, and to determine factors which affect these. MATERIALS & METHODS: Pubmed search identified RCTs published between 2013-2021, recruited people with hip or knee OA. Regression analyses determined participant and trial factors which may have affected recruitment or retention rates. RESULTS: 215 RCTs were included. Mean recruitment rate was 63.2%. Mean follow-up rate was 88.4%. Trials had higher recruitment rates if publicly-funded (Odd Ratio (OR): 1.47; 95% Confidence Intervals (CI: 1.12, 1.92), did not recruited people with medical comorbidities (OR: 0.55; 95% CI: 0.41, 0.73), offered a drug intervention as their experimental intervention (OR: 0.50; 95% CI: 0.29, 0.88), recruited from hospitals (OR: 1.42; 95% CI: 1.07, 1.80) and had shorter follow-up durations (OR: 0.95; 95% CI: 0.91, 0.99). Trials had higher retention rates if their experimental group had lower baseline pain scores (OR: 1.20; 95% CI: 1.02, 1.41), control group had higher pain scores (OR: 0.84; 95% CI: 0.72, 0.99), recruited from fewer sites (OR: 0.98; 95% CI: 0.96, 0.99), with shorter follow-up durations (OR: 0.96; 95% CI: 0.92, 0.99). CONCLUSION: Factors which impact on recruitment and retention rates in OA RCTs include: funding source, baseline pain levels, comorbidity status, location and number of recruitment sites and follow-up duration. These factors should be considered when conducting future OA RCTs