To determine the variation in morning symptoms and in the corresponding monetary equivalents assigned to their reduction.
The sampled (n = 100) rheumatoid arthritis (RA) patients were interviewed twice by a trained interviewer using the same interview, 2 weeks apart. Patients assessed fatigue, pain, and severity of morning stiffness (MS) on waking up and after maximum improvement on a numeric rating scale (NRS). Patients estimated the duration of MS in minutes and reported the number of tender and swollen joints. Patients were also asked to estimate how much they would be willing to pay on a daily basis if pain, duration of MS, and severity of MS when waking up could be reduced by 25, 50, 75, and 100%. Weighted averages of the monetary assessments for symptom reduction were computed.
On average, the NRS values at the first and second assessments were close to each other, except for fatigue and pain, which were significantly lower (p < 0.01) in the second assessment. There was limited within-patient variation, with the majority of symptom assessments within a range of ±10%. Weighted average willingness-to-pay (WTP) estimates were consistent across time points for reduction in pain and MS severity and duration. Changes in symptom assessments were reflected in the WTP estimates.
The duration and severity of MS seemed to be more consistent over time than pain and fatigue. WTP estimates and their changes corresponded closely to changes in symptom assessments.