This was a retrospective cross-sectional study. We included 261 patients with RA, aged 18 to 84 years.
We applied a bottom-up method by retrospectively reviewing individual patient medical records. Patients' demographic characteristics, patient-reported outcome, and clinical parameters were gathered at the time of data collection.
For the calculation of productivity costs, we used the friction cost approach, based on patient absenteeism with a friction period of 130 workdays, with average monthly income used as the denominator. Costs were expressed as a mean value per patient with RA in each HAQ group.