A Systematic Review of Scope and Consistency of Outcome Measures for Physical Fitness in Chronic Kidney Disease Trials

INTRODUCTION: Impaired physical fitness is prevalent in people with chronic kidney disease (CKD), associating with an increased risk of mortality, falls, and hospitalization. A plethora of physical fitness outcomes have been reported in randomized trials. This study aimed to assess the scope and consistency of physical fitness outcomes and outcome measures reported in trials in CKD. METHODS: A systematic review of randomized trials reporting physical fitness outcomes in adults with CKD (not requiring kidney replacement therapy) receiving hemodialysis (HD) or peritoneal dialysis and kidney transplant recipients was conducted. Studies were identified from MEDLINE, Embase, and the Cochrane Library from 2000 to 2019. The scope, frequency, and characteristics of outcome measures were categorized and analyzed. RESULTS: From 111 trials, 87 tests/measurements were used to evaluate 30 outcomes measures that reported on 23 outcomes, categorized into five domains of physical fitness: neuromuscular fitness (reported in 76% of trials), exercise capacity (64%), physiological-metabolic (49%), body composition (36%), and cardiorespiratory fitness (30%). Neuromuscular fitness was examined by 37 tests/measurements including the physical function component of questionnaires (27%), one-repetition maximum (9%), and hand-grip strength (9%). Outcome measures were assessed by lab-based (58% of all trials), field-based (31%), and patient-reported measures (11%), and commonly evaluated at 12 (30%), 26 (23%) and 52 weeks (10%), respectively. CONCLUSION: There is large heterogeneity in the reporting of physical fitness outcomes, with inconsistencies particularly in the definitions of outcome measures. Standardization in the assessment of physical fitness will likely improve the comparability of trial outcomes and enhance clinical recommendations.