To render information on the accuracy of patient-reported indirect cost data compared with payer-derived data of the real indirect costs on a patient-by-patient basis concerning disease-related productivity losses in rheumatoid arthritis (RA).
The assessment of indirect cost data was part of a clinical, multicenter, randomized RA trial. A total of 234 patients of working age with a diagnosis of RA (according to 1987 American College of Rheumatology criteria) were recruited. Demographics of the cohort were mean age 53 years, mean disease duration 8 years, 76% were women, and all had membership in the regional statutory health insurance plan. Every 3 months corresponding indirect cost data were derived for the cohort from a health economic questionnaire for cost assessment in patients with RA and the payer's database over a period of 18 months. Comparative statistical analyses were performed between patient-reported and insurance claims data.
The mean annual productivity losses due to sick leave amounted to 14 and 17 days per patient (questionnaire versus payer data), and productivity losses due to work disability amounted to 3 days (both); monetary valuation renders overall costs of €1,240 and €1,590, respectively. The difference of 17% in overall productivity losses is not significant. Comparison of productivity losses reveals a strong correlation of r = 0.83 in those due to sick leave and of κ = 0.84 in those due to work disability between questionnaire and payer data.
The comparison of questionnaire and payer data shows that RA patients report their productivity losses adequately. Indirect cost assessment should therefore be included in further RA trials and observational studies.