Reliability and Minimal Detectable Change Values for Performance-Based Measures of Physical Functioning in the...

The aim of this study was to determine the relative and absolute reliabilities of 5 key performance-based measures of physical function in the Canadian Longitudinal Study on Aging (CLSA).

An age-stratified subsample of 147 participants from the CLSA who were undergoing their 3-year data collection visit participated in 2 repeat visits (within 1 week). Participants underwent tests of grip strength, 4-m gait speed, Timed Up and Go (TUG), chair rise, and single-leg stance (left, right, mean, maximum). Intraclass correlation coefficients (ICCs), standard error of measurement, and minimal detectable change (MDC) values were calculated.

The relative reliability for grip strength was excellent (ICC = 0.95); the TUG and single-leg stance tests had good reliability (ICC = 0.80 or 0.78-0.82, respectively); gait speed and the chair-rise test had moderate reliability (ICC = 0.64 for both) for participants overall. For participants between 50 and 64 years, TUG and gait speed had poor reliabilities (ICC = 0.38 or 0.33, respectively). For participants aged 75 years and older, the single-leg stance had poor reliability (ICC = 0.30-0.39). The MDC90 was about 6 kg for grip strength, 2.3 seconds for TUG, 0.2 m/second for gait speed, 5.2 seconds for chair rise, and ranged from 22.8 to 26.2 seconds for the single-leg stance.

Among community-dwelling Canadians older than 50 years, the reliabilities of the CLSA measures were moderate to excellent. The TUG and gait speed in the youngest age group, and the single-leg stance in the oldest age group, showed poor reliability. MDC values can be used to interpret changes over time.