[A multicenter cross-sectional study on the health related quality of life of patients with rheumatoid arthritis using a revised Japanese version of the arthritis impact measurement scales version 2 (AIMS 2), focusing on the medical care costs and their associative factors].

OBJECTIVE: To survey the actual conditions of medical care costs incurred by Japanese patients with rheumatoid arthritis, and to investigate impacts of health status, demographic and socioeconomic factors, clinical and laboratory measures, and medications on disease costs.

METHODS: Self-reported health status questionnaires of the revised Japanese version of AIMS 2, and reports on out-of-pocket medical care costs were collected from 1471 patients with classical and definite rheumatoid arthritis recruited through the arthritis study group of Ministry of Public Health and Welfare consisting of eleven arthritis centers across the country during three months from September, 1994. Impacts of health status and other demographic and clinical factors on medical care costs were statistically analyzed by using chi-square tests for categorical variables and Spearman's rank correlation analysis for numerical variables.

RESULTS: 1. Averaged out-of-pocket medical care costs for RA patients was estimated at yen 25,225 ($253.5) per person-month in 1994, in which direct medical care costs accounted for 53.9% and indirect medical care costs accounted for 46.1% of the total. Averaged substantial direct medical care costs including the costs covered by the public health insurance in addition to out-of-pocket costs was estimated at yen 512,000 ($5,140) per person-year based on the averaged 11.8% self-pay rate of the public health insurance in 1994. 2. The distribution curve of the total out-of-pocket medical care costs was highly skewed. Averaged total medical care costs in the 90th, 95th, and 100th percentiles were 4.5, 8.1, and 48 times as large as those in the median percentile, respectively. 3. Out-of-pocket direct medical care costs totaled in the top 1 and 5 percentiles reached 26.6%, and 57.6% of those in whole patients, respectively. 4. Variables most strongly related to the total out-of-pocket medical care costs were work disability in AIMS health status scales, followed by physical disability, rate of functional decline, pain, affect, daily dose of oral prednisolone, global assessment by physician, joint counts, blood levels of CRP, ESR, grip strength, blood concentrations of hemoglobin, age, Steinbrocker's class, sex, and medications, in this order. 5. There was a trend of increase in number of cases of male, middle aged, with lower levels of formal education and annual income, longer disease duration of 20 years or more, and single (male) or separated (female) in marital status, as the total out-of-pocket medical care costs increased. 6. The average rate of missed days due to illness to whole working days of RA patients was estimated at 21.9%. With increase in the rate of missed days, the annual income of RA patients decreased, indicating that the lower annual income of RA patents possibly resulted from their work disabilities. Based on the rate of missed days, the average earning loss due to the illness in RA patients was estimated approximately at yen 650,000 ($6,540) perperson-year, which was equivalent to 1.3 times the average direct medical care costs for RA per person-year.

CONCLUSION: The costs of RA were strongly related to work disability and other health status as represented by AIMS-HRQOL scores. A small number of patents severely disabled shared a disproportionately large part of medical care costs. To reduce the costs, the measures to prevent the development of disability are most important.