Patient-reported health care utilization in rheumatoid arthritis: what level of detail is required?

To investigate the level of detail required in self-reported health care utilization questionnaires for administration to patients with rheumatoid arthritis (RA).

A preliminary questionnaire was developed on the basis of existing tools for use in rheumatic conditions and in-depth interviews with 10 RA patients. Data gathered over 1 year of administration in a clinical setting were then matched to a comprehensive database of payer-reported information. Kappa statistics were calculated for each health care utilization domain. For domains where disaggregation into metric data was potentially preferable, histograms of difference were assessed visually and the strength of association examined using Spearman's rank correlation coefficient.

Patients (n = 136) included in the base case analysis determined the preferred levels of detail for each domain. Physician visits: occurrence of physician visits (yes/no; kappa not applicable) and their number (r = 0.42, P < 0.001). Medication use of the following drug classes (yes/no): disease-modifying antirheumatic drug (DMARD; kappa = 0.68), nonsteroidal antiinflammatory drug (kappa = 0.64), osteoporosis medication (kappa = 0.56), analgesic (kappa = 0.38), and steroid (kappa = 0.83). Further disaggregation into different DMARD classes was recommended (kappa ranging between 1 [use of biologics: yes/no] and 0.67 [use of azathioprine: yes/no]. Imaging: imaging of bones and chest (yes/no; kappa = 0.20). Hospitalization: inpatient episodes (yes/no; kappa = 0.64) and number of inpatient days (r = 0.80, P < 0.001). Transport: costs incurred (yes/no; kappa = 0.13) and amount (r = 0.39, P < 0.001).

The use of highly aggregated items to assess health care utilization in RA is supported. Dichotomous assessment (yes/no) was the preferred level of detail for items in the domains covering medication and diagnostic procedures or tests. Metric data is appropriate in 3 areas: number of physician visits, number of inpatient days, and total expenditure on transportation.