The reliability and validity of the 30-seconds sit-to-stand test and its capacity for assessment of the functional status of hemodialysis patients

PURPOSE:To investigate the validity of the 30-seconds sit-to-stand test (STS-30) and its reliability in hemodialysis patients. METHODS:Patients receiving hemodialysis treatment three times a week for at least six months were evaluated using STS-30, Incremental Shuttle Walking Test, and health-related quality of life by KDQOL-SF questionnaire. The data obtained from the Incremental Shuttle Walking Test were divided into tertiles, and the STS-30 results were compared among tertiles. The accuracy of the STS-30 to identify low exercise capacity was evaluated. A second STS-30 was performed after 6 to 8-weeks for the reliability analyses using Intraclass Correlation Coefficient (ICC). Minimal detectable change scores were calculated. RESULTS:Sixty-three individuals (66.7% men) aged 48.3 years (95%CI 44.6-51.9) were evaluated. There were significant correlations between STS-30, exercise capacity (r = 0.72), and physical domains of health-related quality of life (0.30 ≤ r ≤ 0.51). Tertile 1 of the Incremental Shuttle Walking Test was different from tertiles 2 and 3 for STS-30 [difference of 3.4 repetitions (95%CI 1.5-5.4) and 4.7 repetitions (95%CI 2.8-6.7), respectively]. The value of 12 repetitions was the cut-off points for stratification of individuals with low exercise capacity. The STS-30 had a high test-retest reliability (ICC = 0.93) and the minimal detectable change was 2.1 repetitions. CONCLUSION:The STS-30 is a reliable test, associated with exercise capacity and physical domains of health-related quality of life. Thus, is a valid method for functional evaluation in hemodialysis patients.