Current Best Evidence Recommendations on Measurement and Interpretation of Physical Function in Patients with Chronic Kidney Disease

Chronic kidney disease (CKD) is becoming a serious health problem throughout the world and is one of the most potent known risk factors for cardiovascular disease. Deterioration of physical function is accelerated in patients with CKD to levels that significantly impact on clinically and patient-important outcomes such as morbidity, employment, quality of life and, ultimately, survival. However, meaningful interpretation of the existing physical function-related literature in adult patients with CKD is hindered, possibly due to inconsistent choice of methodology, assessment tools and reporting of data. The current comprehensive review of the literature aims to provide the theoretical rationale and framework for physical function assessment and to identify the prevailing approaches to (i) the characterization (classification and terminology), (ii) interpretation, and (iii) reporting of physical function assessment in people with CKD. Comprehensive assessment of physical function can provide important information about the presence of ‘physiological impairment’ at a body systems level (exercise tolerance under well controlled, laboratory-based procedures), ‘functional limitations’ (physical performance during tasks imitating usual daily, personal or occupational tasks) and ‘functional disability’ (via self-reported physical functioning in the context of a socio-cultural environment). The selection of physical function assessment tools should be guided by the primary purpose of the assessment (e.g. research or routine clinical monitoring), by the overall scientific ‘soundness’ of the chosen tool (e.g. validity, utility, reproducibility, responsiveness characteristics) and by operational factors (e.g. patient collaboration, cost, personnel expertise). Recommendations for tests, methods and protocols are therefore presented, for the assessment of cardiorespiratory and muscular fitness, physical performance and self-reported physical functioning. These recommendations are based on synthesis of available information as derived from controlled exercise training interventions in adult patients with CKD. Special considerations for physical function assessment and suggestions for future research are also addressed. Such an information synthesis might promote greater standardization of the physical function assessment of patients with CKD in routine clinical care or research settings. This would potentially lead to generation of adequate scientific decision-making criteria to help researchers and healthcare providers in selecting the most appropriate measures according to the physical function areas assessed, and to accurately and meaningfully characterize and compare patients’ responses to therapeutic interventions.