Relative and absolute reliability of functional performance measures for adults with dementia living in residential aged care

BACKGROUND: This pilot investigation aimed to assess the relative and absolute test-retest reliability of commonly used functional performance measures in older adults with dementia residing in residential aged care facilities.

METHODS: A total of 12 participants were tested on the Short Physical Performance Battery (SPPB), the Balance Outcome Measure for Elder Rehab (BOOMER), hand grip strength, anthropometric measures and Bio-electric Impedance Analysis (BIA). This study utilized a seven-day test-retest evaluation. Intra-class Correlation Coefficients (ICC) were used to assess relative reliability, Typical Error of Measurement (TEM) was used to assess the absolute reliability, and Bland-Altman plots were used to assess group and individual levels of agreement.

RESULTS: With the exception of Standing Balance (ICC = 0.49), 2.4-m walk (ICC = 0.68), functional reach (ICC = 0.38), and static timed standing (ICC = 0.47), all measures demonstrated acceptable (>0.71) ICCs. However, only the anthropometric measures demonstrated acceptable levels of absolute reliability (>10% TEM). Bland-Altman analysis showed non-significant (p > 0.05) mean differences, and eight out of the 17 measures showing wide Limits of Agreement (LoA).

CONCLUSIONS: Current measures of functional performance are demonstrably inappropriate for use with a population of older adults with dementia. Authors suggest aligning current measurement strategies with Item Response Theory as a way forward.