The 1-min sit-to-stand test-A simple functional capacity test in cystic fibrosis?

Background: We aimed to assess the measurement properties and the minimal important difference (MID) of the 1-min sit-to-stand (STS) test in cystic fibrosis (CF). Methods: Patients with CF were tested during a pulmonary rehabilitation program. Five STS tests were performed during the program; two tests at the beginning (STS₀ and STS₁) and three tests at the end (STS_2a-2c). Exercise capacity, pulmonary function, and health-related quality of life (HRQoL) and patient-reported health status were measured at the beginning and end of the program. We calculated overall mean, standard deviation, coefficient of variation (CV), and intraclass correlation coefficient (ICC) of the STS test. The MID was calculated using anchor-based and distributional methods. Results: Fourteen participants (8 female, mean age 30.4±6.1years) were included. STS test performance increased significantly from STS₀ to STS₁ indicative of a learning effect. Test-retest reliability for the subsequent STS_2a-2c tests was excellent (ICC 0.98, 95% CI 0.96-0.99). The estimated MID for the STS test was 5 repetitions. STS test performance was responsive to change (effect size of 0.97) and correlated with exercise capacity (r =0.63-0.73) and with the physical functioning HRQoL scale (r =0.72). Conclusions: The 1-min STS test appears to be a reliable, valid, and feasible test to measure functional capacity in patients with CF.