Identifying early decline of daily function and its association with physical function in chronic kidney disease: performance-based and self-reported measures

OBJECTIVE: To verify self-reported basic and instrumental activities of daily living (IADL) with a disability and the results of performance-based tests (namely the Taiwan performance-based IADL (TPIADL), the 2-minute step test (2MST), the 30-second chair-stand test (30-s CST), and handgrip dynamometer measurement) to identify disability early and assess the associations with functional fitness in patients with advanced chronic kidney disease (CKD). METHODS: A cross-sectional study of 99 patients with stage 4-5 CKD and 57 healthy elderly adults were recruited. Self-reported measures were used to collect information on basic (Barthel Index) and IADL (Lawton-Brody scale). Objective measures of the TPIADL and functional fitness (2MST, 30-s CST, handgrip dynamometer) were also assessed. RESULTS: Only IADL, as detected by the TPIADL, were impaired to a greater extent in the CKD patients than those of healthy elderly adults. Among all the patients with CKD, a greater impairment in the TPIADL remained statistically associated with a lower ability in the 2MST. A one step increase in the 2MST score was significantly associated with an improvement of 0.2 s in the total performance time of the TPIADL. CONCLUSION: Performance-based measures, such as the TPIADL, may detect a functional limitation before it becomes measurable by traditional self-reported basic and IADL scales; functional limitation is mainly associated with cardiac endurance for advanced CKD.