Minimal clinically important difference (MCID) has become the most important psychometric factor for interpreting change in individual's responses over time from the patient's perspective, evaluating study results and planning sample sizes. The purpose was to synthesize and critically appraise MCID of the most frequently used hip-, knee-, foot-, and ankle-specific patient-reported outcomes (PROs).
A search was conducted on PubMed, Cochrane Library, and Web of Science from each site's respective inception through January 2019 for MCID in 25 PROs. The studies reporting their results with anchor-based method were included.
228 full-text articles were assessed for eligibility, and 48 were included in the final evaluation. Our synthesis provides a comprehensive assessment of MCID for 16 disease or joint specific PROs. MCID of the Western Ontario and McMaster Universities Index (33.3%), International Knee Documentation Committee Subjective Knee Form (14.5%) and Knee Injury, and Osteoarthritis Outcome Score (14.5%) was found to be the most commonly presented PROs. The studies mainly (85%) used the receiver operating curve analysis to elicit MCID.
MCID is increasingly used as a measure of patient's improvement. However, MCID varied based on the analytic methods, study population, type of disease, the baseline status, change in values and treatments, and patient demographics. Therefore, it should be interpreted with caution.