Test-retest reliability of subclinical status for functional limitation and disability

OBJECTIVE: Subclinical status for functional limitation and disability help explain pathways to difficulties with functional limitation and disability, but data on their measurement stability are minimal. We evaluated the reproducibility of measuring subclinical status in a random subset of 92 community-dwelling St. Louis African Americans aged 49 to 65 years old. METHODS: We examined test-retest reliability of subclinical status using Fried's measurement method of changing either the frequency or method of task performance for five functional limitations, three basic activities of daily living (ADLs), and four instrumental ADLs, as well as summary scales reflecting these three constructs. We also performed sensitivity analyses of test-retest interval and alternative definitional approaches (using only method, only frequency, or both). RESULT: Weighted kappas for individual tasks across three performance levels (high functioning, subclinical status, and task difficulty) indicated moderate agreement for one task and substantial agreement for 11 tasks. Intraclass correlation coefficients for the three scales demonstrated outstanding agreement. The most reproducible definition of subclinical status involved the either/or method. DISCUSSION: Excellent test-retest reproducibility was demonstrated in this population-based sample of late middle-aged African Americans using Fried's method of measuring subclinical status.     

Effect of subclinical status in functional limitation and disability on adverse health outcomes 3 years later

BACKGROUND: This article examines the effect of self-reported, baseline subclinical status (i.e., independent but adaptive performance) for functional limitation and disability on adverse health outcomes. METHODS: Nine hundred ninety-eight African-American men and women aged 49-65 years received in-home evaluations at baseline, and 853 were re-evaluated 3 years later. Baseline subclinical status was ascertained for five lower body tasks and seven activities of daily living (ADLs)/instrumental ADLs (IADLs). Outcomes included difficulty with lower body limitations, ADLs/IADLs, physical performance, physician visits, hospitalization, nursing home placement, and mortality. RESULTS: The baseline proportion of subclinical status evidence for the five lower body items was 0.33 (standard deviation [SD] = 0.20), and for the seven ADLs/IADLs was 0.20 (SD = 0.30). Significant independent effects of subclinical status for lower body limitations were observed on physician visits and hospitalization. Significant independent effects of subclinical status for ADLs/IADLs were observed on ADLs/IADLs and physician visits. CONCLUSIONS: Subclinical status for functional limitation and disability independently predicts several subsequent adverse health outcomes, although the effects of the latter (ADLs/IADLs) are stronger. Interventions to reduce frailty should focus on self-reported subclinical status as an early warning system.