Design and validation of a methodology using the International Classification of Diseases, 9th Revision, to identify secondary conditions in people with disabilities

Objective: To design and validate a methodology that identifies secondary conditions using International Classification of Disease, 9th Revision (ICD-9) codes. Design: Secondary conditions were identified through a literature search and a survey of Washington State physiatrists. These conditions were translated into ICD-9 codes and this list was then validated against a national sample of Medicare survey respondents with differing levels of mobility and activities of daily living (ADL) disability. Setting: National survey. Participants: Participants (N=9731) in the 1999 Medicare Current Beneficiary Survey with no, mild, moderate, and severe mobility and ADL disability. Interventions: Not applicable. Main Outcome Measure: Percentage of survey respondents with a secondary condition. The secondary conditions were grouped into 4 categories: medical, psychosocial, musculoskeletal, and dysphagia related (problems associated with difficulty in swallowing). Results: Our literature search and survey of 26 physiatrists identified 64 secondary conditions, including depression, decubitus ulcers, and deconditioning. Overall, 70.4% of all survey respondents were treated for a secondary condition. We found a significant relation between increasing mobility as well as ADL disability and increasing numbers of secondary conditions (chi(2) test for trend, P < .001). This relation existed for all categories of secondary conditions: medical (chi(2) test for trend, P < .001) hosocial (chi(2) test for trend, P < .001), musculoskeletal test for trend, P < .001), and dysphagia related (chi(2) test for trend, P < .001). Conclusions: We created a valid ICD-9-based methodology that identified secondary conditions in Medicare survey respondents and discriminated between people with different degrees of disability. This methodology will be useful for health services researchers who study the frequency and impact of secondary conditions. (c) 2005 by American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation.