Reliability and validity of the five-repetition sit-to-stand test in adult kidney transplant recipients

Abstract

Background/Aims: To investigate the reliability and validity of the five-repetition sit-to-stand test (FRSTST) to assess lower-limb muscle strength and physical function in adult kidney transplant recipients. Methods: A cross-sectional, observational study was conducted in a secondary care centre. A convenience sample of 56 adult kidney transplant recipients were recruited following a 6-week post-transplantation recovery period. The participants were within their first 18 months of kidney transplantation. The measurements included FRSTST times, myometer measurements of isometric quadriceps muscle strength, 60-second sit-to-stand test (STS60) scores, and Duke Activity Status Index (DASI) scores. Findings: Inter- and intratester reliability of the FRSTST were excellent (intraclass correlation coefficients 0.997 and 0.970, respectively). The standard error of measurement and the minimal detectable change at 95% confidence level were 0.9 and 2.5 seconds, respectively. The best FRSTST scores by the two testers had non-significant, weak correlations with the isometric quadriceps muscle force (Spearman's rho, rs=-0.04, p=0.76), and quadriceps muscle torque (rs=0.04, p=0.76). The FRSTST correlated significantly with the STS60 (rs=-0.90, p=0.001) and DASI scores (rs=-0.49, p=0.001). Conclusions: The FRSTST can be considered to be a reliable test of physical function for adult kidney transplant recipients, but may not be used as a surrogate measure of lower limb muscle strength in this population.