Validity of the revised impact on Family (IOF) Scale

Objective To assess psychometric properties of the revised 15-item Impact on Family (IOF) Scale. Study design A secondary analysis of items using data collected from 252 parents during an earlier randomized clinical trial. Results Exploratory factor analysis and confirmatory factor analysis identified a single factor with factor loadings similar to that of IOF developers. The one factor accounts for 45.7% of the sample variance. An Item Response Theory analysis found that 11 of the 15 items had a values greater than 1.00, with good to excellent item characteristic and item information curves. The test information and measurement error curves for the entire IOF were excellent. Construct validity of the IOF also was supported. Parent IOF scores correlated in the expected directions with maternal mood (r = -0.50), sibling behavior problems (r = -0.35), and severity of illness (r = 0.31) and were associated with family socioeconomic status (t = -4.5, all P < .001). Conclusions This study provides independent support for validity and reliability of the revised IOF scale. This scale is a promising, easy-to-use instrument for the measurement of impact of illness and disability on families of children with chronic illness or disability.