Identification of work disability in rheumatoid arthritis: physical, radiographic and laboratory variables do not add explanatory power to demographic and functional variables.

Work disability, a common problem in rheumatoid arthritis (RA), is known to be associated with demographic variables such as occupation, age, and formal education, as well as with disease duration. However, physical, radiographic and laboratory variables, which are included in the traditional "medical model" of work disability and collected routinely in the application process, have not been studied for their capacity to explain whether patients are working or receiving work disability payments. A cross-sectional database which included an extensively characterized group of patients with RA was examined to determine possible associations of demographic, functional, physical, radiographic and laboratory variables with work disability status. All these variables differed in patients who were receiving work disability payments and those who were working full time, but in multivariate analyses, work or disability status was best identified by demographic and functional variables. Physical, radiographic, and laboratory data did not add significantly to explanation of work disability status beyond the demographic and functional variables and disease duration, despite the fact that receipt of disability payments was used as the criterion for work disability status.