Title: Patient versus Physician Joint Counts in Rheumatoid Arthritis Utilizing a Unique Self-Joint Examination Tool
Daisy H. Bang1, Yomei Shaw2, Chris L. Amity1, Kelley A. Reckley1, Ilinca D. Metes1 and Marc C. Levesque1
University of Pittsburgh, Pittsburgh, PA, School of Medicine, Department of Medicine, Division of Rheumatology and Clinical Immunology1, School of Public Health, Department of Epidemiology2
Background:
The quantitative assessment of disease activity has been endorsed by the American College of Rheumatology (ACR) to improve rheumatoid arthritis (RA) outcomes. To facilitate more quantitative assessments of disease activity, we created a unique self-joint examination tool and compared patient and physician joint assessments in RA subjects using this tool.
Methods:
Subjects were part of the University of Pittsburgh Rheumatoid Arthritis Comparative Effectiveness Research (RACER) registry. Subjects performed a self-joint count on a computer tablet utilizing line-drawings of human figures incorporating both audio and written instructions on assessment of 28 joints (bilateral shoulders, elbows, wrists, knees, and first through fifth PIP and MCP joints) for tenderness and swelling. Physicians performed independent joint counts at each visit and serum C-reactive protein (CRP) concentrations were measured. Comparisons between patient and physician individual and total swollen and tender joint counts and between patient and physician DAS28-CRP scores were made using t tests and Cohen’s kappa statistic.
Results:
There were 516 paired patient and physician joint counts for RA subjects completing the self-joint exam for the first time. CRP was measured in 364 patients. Patient vs. physician total swollen (mean ± SD, 3.58 ± 5.99 vs. 2.68 ± 4.01; p = 0.0003) and tender (mean ± SD, 5.94 ± 7.28 vs. 2.40 ± 3.96; p<0.0001) joint counts were significantly higher. Mean patient vs. physician DAS28-CRP scores were also significantly higher (mean ± SD, 3.49 ± 1.50 vs. 3.02 ± 1.25; p < 0.0001). Cohen’s kappa statistic of interrater reliability between patients and physicians for individual tender joint counts ranged from 0.10 to 0.39; for swollen joints it ranged from 0.12 to 0.36. Interrater reliability was greatest for the knees, wrists and the second and third MCP joints. DAS28-CRP scores calculated from the patient and physician joint counts were used to categorize patients into remission, low, moderate or high disease activity. Cohen’s kappa for patient versus physician categorization into remission/low disease activity or moderate/high disease activity based on DAS28-CRP scores was 0.60. In 291 cases (88%), the categorizations agreed. In 73 cases (18%), the categorizations differed. In 52 (13%) of the discrepant cases, the patient's joint count indicated moderate/high disease activity while the physician's did not; in 21 (5%) of the discrepant cases the reverse was noted.
Conclusion:
On average, patients reported significantly higher tender and swollen joint counts with greater differences in tender joint counts between patients and physicians. The difference in joint counts resulted in significantly higher DAS28-CRP scores and higher DAS28-CRP disease activity categorization in some cases with discrepancies large enough to potentially alter treatment decisions. These findings suggest that despite the use of a self-joint count tool that incorporates training, mannequin-formats, and a computer tablet interface, patient and physician joint counts still differ. Analysis of the factors that characterize discordant patient-physician pairs will help to inform next steps.