Self-reported painful joint count and assessor-reported tender joint count as instruments to assess pain in hand osteoarthritis

Objectives. To evaluate self-reported and assessor-reported joint counts for pain and their value in measuring pain and joint activity in hand OA patients. Methods. A total of 524 patients marked painful joints on hand diagrams. Nurses assessed tenderness upon palpation. Pain was measured with a visual analogue scale pain and the Australian/Canadian hand OA index subscale pain. Synovitis and bone marrow lesions in right hand distal/proximal interphalangeal joints on MRI served as measure of joint activity. Agreement was assessed on the patient (intraclass correlation coefficient, Bland-Altman plot) and joint level (percentage absolute agreement). Correlations with measures of pain and joint activity were analysed, and joint level associations with synovitis/bone marrow lesions were calculated. Results. Self-reported painful joint count (median 8, interquartile range 4-13) was consistently higher than assessor-reported tender joint count (3, 1-7). Agreement between patients and nurses on overall scores was low. Percentage absolute agreement on the joint level was 61-89%. Joint counts correlated similarly but weakly with measures of pain and joint activity (r = 0.14-0.38). On the joint level, assessor-reported tenderness was more strongly associated with synovitis/bone marrow lesions than self-reported pain. Conclusion. In hand OA, self- and assessor-reported joint counts cannot be used interchangeably, and measure other pain aspects than questionnaires. Assessor-reported tenderness was most closely related to MRI-defined joint activity.