Background/Purpose:

Patient-reported joint counts (JCs) might improve the efficiency and consistency of disease monitoring, self-management and early recognition of changes in disease activity in rheumatoid arthritis (RA).

To assess the reliability and validity of patient-reported JCs as compared to physician JCs in recent onset RA and to identify determinants of disagreement.

Methods:

Data from 795 recent-onset (< 1 year) RA patients from the Canadian early arthritis cohort (CATCH) were used. Patient-reported tender (T) and swollen (S) JCs were derived from a 40-joint homunculus and the 16-joint RA-disease-activity-index (RADAI) mannequin. Physician JCs were abstracted from the TJC68 and SJC66. Inter-rater reliability of patient TJCs and SJCs as compared with corresponding physician JCs was assessed, using intra-class correlation coefficient (ICC) two-way random effects model. Agreement on activity of joint areas was assessed by kappa. Pearson correlation coefficients were determined between the patient JCs counts separately and incorporated into the patient-disease-activity-score (pDAS) and routine-assessment-of-patient-index-data (RAPID4) with DAS28 and health assessment questionnaire (HAQ). Determinants of disagreement with the physician (over- or underestimation >=1 joint) were identified by multinomial logistic regression.

Results:

The reliability of the patient TJC40 was moderate (ICC 0.61; 95%CI 0.51-0.69), with lower ICC for the 16 joint RADAI-derived TJC (ICC 0.51; 95%CI 0.21-0.68) and patient SJC40 (ICC 0.52; 95%CI 0.46-0.57). Positive agreement among joint regions ranged from 47%-82% (kappa 0.26-0.51) for tenderness and from 33%-60% (kappa 0.10-0.44) for swelling, being highest for tenderness in large joints (figure 1). Differences between patient and physician JCs were lowest in patients in DAS28 remission or low disease activity (figure 2). Determinants of disagreement on TJC were lower age, male gender, higher DAS28, disability and depressed mood. Disagreement on SJC was associated with male gender and higher DAS28. Correlations of DAS28 and HAQ with the PDAS (r 0.90; r 0.73, resp.) and RAPID4 (r 0.72; r 0.85, resp.) were higher than with the separate patient SJC40 (r 0.54; r 0.47, resp.) and TJC40 (r 0.57; r 0.54, resp.).

Conclusion:

In recent onset RA, patient-reported JCs demonstrate moderate reliability and validity. Patient JCs can be incorporated in patient-reported outcomes in studies addressing remission induction and treatment withdrawal strategies to investigate their ability to detect changes in disease activity and discriminate flares.