Standards of Comparison and Discordance in Rheumatoid Arthritis Global Assessments Between Patients and Clinicians.

OBJECTIVE: Patient-physician discordance in health status ratings may arise because patients use temporal comparisons (comparing their current status with their previous status), while clinicians use social comparisons (comparing this patient's status to that of other patients, or to the full range of disease severity possible) to guide their assessments. We compared discordance between patients with rheumatoid arthritis (RA) and clinicians, using either the conventional patient global assessment (PGA) or a rating scale with 5 anchors describing different health states. We hypothesized that discordance would be smaller with the rating scale because clinicians likely used similar social comparisons when making global assessments.
METHODS: We prospectively studied 206 patients with active RA and assessed the PGA (range 0-100), rating scale (range 0-100), and evaluator global assessment (EGA; range 0-100) on each of 2 visits (total visits = 401). We compared the PGA/EGA discordance and the rating scale/EGA discordance at each visit.
RESULTS: The mean ± SD PGA/EGA discordance was 8.5 ± 22.4, and the mean ± SD rating scale/EGA discordance was 2.3 ± 24.0. The intraclass correlation, measuring agreement, was higher between the rating scale and EGA than between the PGA and EGA (0.39 versus 0.31). Agreement was larger at low levels of RA activity on both pairs of measures.
CONCLUSION: Discordance between patients' global assessments and evaluators' global assessments was smaller when patients used a social standard of comparison than when they marked the PGA, suggesting that differences in standards of comparison contribute to patient-clinician discordance when the PGA is used.