Minimal change is sensitive, less specific to recovery: a diagnostic testing approach to interpretability

Objective

The pursuit of interpretability of longitudinal measures of patient outcome has led to several methods for defining minimal amounts of change or final states that are important. Little is known about the best method. The purpose of this study was to directly compare methods using diagnostic utility to evaluate their usefulness.

Study Design and Setting

Secondary analysis of longitudinal cohort data of persons attending physiotherapy for shoulder pain. Disability of the arm, shoulder, and hand outcome fielded at baseline and 3 months. Published methods were used to define positive response in scores: minimal change, final state, and combined change and final state. Proportions described as improved were compared (Kappa) and diagnostic testing techniques used to evaluate the strengths of each.

Results

Only moderate agreement was found between methods (Kappa = 0.47). Minimal clinically important differences were most sensitive but not specific. Final states were less sensitive, more specific, and most accurate. Combinations were slightly less specific.

Conclusion

A new approach allowed us to evaluate the relative merits and risks of different approaches to interpreting longitudinal patient outcomes. Our study points to a combination of change greater than error and/or a final score within general population norms as being the most clinically sensible with strong diagnostic accuracy.     

Defining Failure in Primary Total Joint Arthroplasty: The Minimal Clinically Important Difference for Worsening Score

BackgroundWe define the value of the Minimal Clinically Important Difference for Worsening (MCID-W) for Patient-Reported Outcomes Measurement Information System Physical Function short form 10-a (PROMIS-PF-10a) score for primary total joint arthroplasty (TJA) of the hip and knee and describe the risk factors for patients scoring worse than the MCID-W.MethodsThis retrospective study was performed using 3414 primary TJA patients. PROMIS-PF-10a scores were collected at the preoperatively and postoperatively, and patients were classified based on reaching Minimal Clinically Importance Difference for Improvement (MCID-I), MCID-W, or “no significant change” after TJA (scores betweex`n MCID-W and MCID-I). MCID-W and MCID-I values were determined by a distribution method. The association between numerous variables and scoring worse than the MCID-W of PROMIS-PF-10a was then evaluated through multiple logistic regression. A threshold for preoperative PROMIS-PF-10a score predicting decline past MCID-W was determined using the Youden index and receiver operating characteristic curve.ResultsThe MCID-W for TJA was ?1.89. Notably, increasing length of stay (odds ratio [OR] 1.073, 95% confidence interval [CI] 1.029-1.119, P < .001) and increasing preoperative PROMIS-PF-10a scores (OR 1.117, 95% CI 1.091-1.144, P < .001) were associated with increased likelihood of decline past the MCID-W of the PROMIS-PF-10a for TJA compared with patients who achieved the MCID-I. A community hospital with a dedicated joint replacement center was associated with a decreased risk for decline past the MCID-W (OR 0.601, 95% CI 0.402-0.899; P = .013).ConclusionWe described the MCID-W value (?1.89) for the PROMIS-PF-10a questionnaire for knee and hip TJA and associated patient- and hospital-level risk factors for failure after TJA. Healthcare funding initiatives should be directed toward modifiable factors associated with clinically significant worse outcomes after TJA.