The aims of this study were to determine the within-patient variation in the duration of morning stiffness (MS) over 1 year and the corresponding monetary equivalents assigned to its changes using the willingness-to-pay (WTP) methodology.
A sample of 100 patients with rheumatoid arthritis (RA) was drawn from the register of the Hospital District of Southwest Finland. Subjects were interviewed by telephone on recruitment and 1 year later, using the same structured questionnaire. The subjects were asked to estimate in minutes the typical duration of their MS during the previous week. Sociodemographic background data and subjects' WTP for a 25, 50, 75, and 100% reduction in MS duration were requested, and years with RA diagnosis and serological data were obtained from hospital records.
After 1 year, there was a reduction in average MS duration from 44.7 min to 39.0 min (ns); duration was reduced in 35% of patients, unchanged in 35%, and prolonged in 30%. Changes in MS duration were reflected by within-patient variation in WTP estimates. In linear regression models, change in duration of MS significantly (p < 0.03) explained the variation in change of WTP for symptom reduction.
WTP methodology produces consistent monetary values to assess the relative values patients with RA place on reduction in duration of MS.