A patient-derived disease activity score can substitute for a physician-derived disease activity score in clinical research

Objective. Joint counts have a central role in assessing disease activity i n rheumatoid arthritis (RA). They are usually undertaken by physicians or n urses. We investigated whether joint counts can be devolved to patients and evaluated the use of a patient-derived Disease Activity Score (DAS). Methods. One hundred RA patients attending a specialist unit were evaluated , comparing joint counts by a physician with patient-assessed joint counts and DAS derived from both methods. They were related to other measures of d isease activity in the European League Against Rheumatism (EULAR) core data set and with the Rheumatoid Arthritis Disease Activity Index (RADAI; a val idated patient self-assessment index). Results. Regression analysis showed no significant differences between a ph ysician's and patient's joint counts and DAS. There were middle to high cor relations between patient and physician assessments of tender joints and sw ollen joints; using R-2, this explained 70% of the variance for tender join ts and 40% for swollen joints. Kappa analysis showed good agreement between physician and patient assessments of individual joint tenderness (kappa va lues 0.49-0.84). There was lower agreement for individual swollen joints (k appa values 0.02-0.61). Physician DAS and patient DAS had a similar correla tion with the Health Assessment Questionnaire (HAQ) (r = 0.50 and r = 0.48, respectively). Conclusion. The agreements between physician and patient assessments are su fficient to allow patients' assessments to be used for clinical research. T his is especially the case with a patient-derived DAS. However, the results are not directly interchangeable and further studies are needed before pat ients' assessments are used to guide clinical practice.