A Study of the Reliability, Validity, and Precision of Scales to Measure Chronic Functional Limitations Due to Poor Health
Results of psychometric studies of 14 questionnaire items used to define limitations due to poor health are reported. Self-administered questionnaires gathered data from 1,209 persons. Data were used to study scalability of items, test-retest reliability of alternate forms of scales, validity of scales in relation to 13 health status variables and age, and precision of scales in detecting differences in functional limitations. Three scales pertaining to chronic limitations in mobility, physical activity, and social role activity functions satisfied the criteria of scalogram analysis. Four-month test-retest reliability estimates for alternative forms were very high. Strong associations (some curvilinear) were observed among functional limitations scales, and between these scales and survey measures of physical abilities, general health perceptions, health worry/concern, chronic disease conditions, and age. Measures of physical abilities and functional limitations appeared to define opposite ends of a function-dysfunction continuum.