This paper aims to evaluate the relationship of patient-reported tender and swollen joints with active inflammation as detected by power Doppler (PDUS) and whether this relationship is affected by significant joint damage.
Fifty rheumatoid arthritis patients self-assessed 28 tender and swollen joints and were followed by PDUS assessment. Relationship of tender and swollen joints with active synovitis (PDUS 'gold standard') was assessed at the joint level by: a) percentage agreement at each PDUS semiquantitative grade (grade 1 to 3), b) positive likelihood ratio (LR) of agreement with PDUS, and c) LR of agreement with PDUS according to radiographic damage (significant erosive disease vs. non-erosive disease). Correlation of tender and swollen joint counts with disease activity markers was analysed by Spearman's. Sensitivity analyses examined the influence of disease activity or global pain on level of agreement at the joint level.
Of joints with significant active inflammation (e.g. grade 3 PDUS), patients identified 75% as tender and 63% as swollen. Swollen joints showed strong association at the joint level with active synovitis when there was no significant radiographic damage (LR 2.54, 95%CI 1.93-3.34), but with no significant radiographic damage (LR 1.32, 95%CI 0.75-2.32). Swollen joint counts were statistically correlated with PDUS-DAS28 and CRP, but not PDUS score. Sensitivity analysis showed better agreement of tender and swollen joints with active synovitis when DAS28 was ≤ 3.2 and when patient global pain was <50mm on visual analogue scale.
The relationship between patient-reported joints and active synovitis is stronger in the setting of low disease activity without erosive disease, affected also by degree of reported global pain. Further longitudinal studies of patient-reported joints are needed.