The ‘minimum clinically important difference’ in frequently reported objective physical function tests following a 12-week renal rehabilitation exercise intervention in non-dialysis chronic kidney disease

Objective Chronic kidney disease (CKD) 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' (MCID), 'the smallest change that is important to the patient', for commonly reported physical function tests. Design Non-dialysis CKD patients completed 12-weeks of a combined aerobic (plus resistance training). The incremental shuttle walking test (ISWT), sit-to-stand-5 (STS-5) and 60 (STS-60), estimated 1 repetition maximum (e1RM) for the knee extensors, and VO2peak were assessed. After the intervention, patients rated their perceived change in health. Both anchor- and distribution-based MCID approaches were calculated. Results The MCID was calculated as follows: ISWT, +45m; STS-5, -4.2 seconds; VO2peak, +1.5 ml/kg/min. Due to comparable increases in 'anchor' groups, no MCID was estimated for the STS-60 or e1RM. Conclusion We have established the MCID in CKD 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 following exercise interventions where these tests are employed. These MCIDs can be used to power future studies to detect clinically important changes. Corresponding author: Dr. Thomas J Wilkinson, Leicester Kidney Exercise Team, Department of Infection, Immunity and Inflammation, University of Leicester, United Kingdom, LE5 4PW. Email: t.j.wilkinson@leicester.ac.uk Author disclosures The authors report no conflicts of interest. Preliminary results from this analysis have been presented at the American Society of Nephrology Kidney Week 2016 (Chicago). Funding statement This work was gratefully part-funded by the Stoneygate Trust. The research was supported by the National Institute for Health Research (NIHR) Leicester Biomedical Research Centre (BRC). Copyright © 2018 Wolters Kluwer Health, Inc. All rights reserved.

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