The "Minimum Clinically Important Difference" in Frequently Reported Objective Physical Function Tests After a 12-Week Renal Rehabilitation Exercise Intervention in Nondialysis Chronic Kidney Disease

Abstract

Objective: Chronic kidney disease patients are characterized by impaired physical function. The goal of exercise-based interventions is an improvement in functional performance. However, improvements are often determined by "statistically significant" changes. We investigated the "minimum clinically important difference," "the smallest change that is important to the patient," for commonly reported physical function tests.

Design: Nondialysis chronic kidney disease patients completed 12-wks of a combined aerobic (plus resistance training). The incremental shuttle walking test, sit-to-stand 5 and 60, estimated 1-repetition maximum for the knee extensors, and VO2peak were assessed. After the intervention, patients rated their perceived change in health. Both anchor- and distribution-based minimum clinically important difference approaches were calculated.

Results: The minimum clinically important difference was calculated as follows: incremental shuttle walking test, +45 m; sit-to-stand 5, -4.2 secs; VO2peak, +1.5 ml/kg per min. Because of comparable increases in "anchor" groups, no minimum clinically important difference was estimated for the sit-to-stand 60 or estimated 1-repetition maximum.

Conclusions: We have established the minimum clinically important difference in chronic kidney disease for common tests of physical function. These values represent the minimum change required for patients to perceive noticeable and beneficial change to their health. These scores will help interpret changes after exercise interventions where these tests are used. These minimum clinically important differences can be used to power future studies to detect clinically important changes.

To claim cme credits: Complete the self-assessment activity and evaluation online at http://www.physiatry.org/JournalCME CME OBJECTIVES: Upon completion of this article, the reader should be able to: (1) Define the "minimum clinically important difference"; (2) Distinguish between concepts of minimum clinically important difference, "minimal detectable change,", and "statistically significant change"; and (3) Interpret other study findings and their own results in the context of the minimum clinically important difference rather than statistically significant changes.

Level: Advanced ACCREDITATION: The Association of Academic Physiatrists is accredited by the Accreditation Council for Continuing Medical Education to provide continuing medical education for physicians.The Association of Academic Physiatrists designates this Journal-based CME activity for a maximum of 1.0 AMA PRA Category 1 Credit(s)™. Physicians should only claim credit commensurate with the extent of their participation in the activity.