Measuring disability with parsimony: evidence for the utility of a single item

Purpose: To provide evidence for the utility of a single item measure designed to quantify disability in the past 30 days. Method: Australian data from studies comprising a community-dwelling elderly sample (N=328) and a sample of chronic osteoarthritis (OA) patients (N=119) are reported. Degree of disability was classified as 0-30 days, 0 vs. 1 or more days, and 0-9 vs. 10 or more days. Associations between disability and a range of demographic, health-related, and psychological variables were assessed. Results: Participants with OA reported a significantly higher level of disability than participants from the community sample regardless of how disability was classified. Modest levels of association were noted between the number of disability days (0-30) and both health and psychological indices in both samples. The three alternative classifications of disability made little difference to the significance of associations. On balance, the comparison of 0-9 vs. 10 or more days appeared the more predictive classification of disability. Conclusions: The performance of the single item measure of disability was generally very satisfactory. Future investigations into the clinical application of the item across a range of patient groups are encouraged.