Abstract
Background
This article reviews four commonly used approaches to assess patient responsiveness to a treatment or therapy [Return To Normal (RTN), Minimal Important Difference (MID), Minimal Clinically Important Difference (MCID), OMERACT-OARSI (OO)], and demonstrates how each of the methods can be formulated in a multi-level modelling (MLM) framework.
Methods
Data from the Arthroplasty Pain Experience (APEX) cohort study was used. Patients undergoing total hip and knee replacement completed the Intermittent and Constant Osteoarthritis Pain (ICOAP) questionnaire prior to surgery and then at 3, 6 and 12 months after surgery. We compare baseline scores, change scores, and proportion of individuals defined as “responders” using traditional and multi-level model (MLM) approaches to patient responsiveness.
Results
Using existing approaches, baseline and change scores are underestimated, and the variance of baseline and change scores overestimated in comparison to MLM approaches. MLM increases the proportion of individuals defined as responding in RTN, MID, and OO criteria compared to existing approaches. Using MLM with the MCID criteria reduces the number of individuals identified as responders.
Conclusion
MLM improves the estimation of the standard deviation of baseline and change scores by explicitly incorporating measurement error into the model, and avoiding regression to the mean when making individual predictions. Using refined definitions of responsiveness may lead to a reduction in misclassification when attempting to predict who does and does not respond to an intervention, and clarifies the similarities between existing methods.
Approvals
The APEX trials were registered as an International Standardised Randomised Controlled Trial (96095682), approved by Southampton and South West Hampshire Research Ethics Committee (09/H0504/94) and all participants provided informed written consent.
