medwireNews: Tender joints in patients with rheumatoid arthritis (RA) may not be a suitable indicator of inflammation, study findings show.
“Our study supports previous studies which question the specificity of tender joint assessment in the evaluation of inflammation in patients with established RA and highlight the importance of exploring whether non-inflammatory causes may explain the lack of achieving CDAI or ACR/EULAR Boolean remission in patients with predominantly tender joints,” explain Hilde Berner Hammer (Diakonhjemmet Hospital, Oslo, Norway) and team.
They propose: “If patients with predominantly tender joints do not reach [composite disease activity scores] remission, objective assessments of inflammation should be performed.”
The team analyzed data from 110 patients with RA participating in the Nordic multicenter TOZURA study. The patients were taking subcutaneous tocilizumab and had an inadequate response or intolerance to conventional DMARDs.
The majority (64%) of patients had tender joints at baseline, according to tender-swollen joint difference (TSJD). At 24 weeks, 38.5% of patients had predominantly tender joints (median three tender, zero swollen joints), while 61.5% had predominantly swollen joints (zero tender, one swollen joint).
The researchers report that, “[i]mportantly, only a few” patients with predominantly tender joints achieved CDAI and ACR/EULAR Boolean remission after 24 weeks, at 3.3% and 2.2%, respectively, none of whom had a TSJD of 2 or more. By contrast, the corresponding remission rates among patients with predominantly swollen joints were 36.3% and 28.6%.
Despite patients with predominantly tender joints seldom achieving CDAI and ACR/EULAR Boolean remission, they were as likely as those with predominantly swollen joints to achieve Doppler remission by week 24, at a rate of 26.4% in both groups. They also had significantly lower gray scale (6 vs 10 points) and Doppler (0 vs 1 point) ultrasound synovitis scores than patients with predominantly swollen joints.
Yet patient-reported outcomes (PROMs) were significantly worse among patients with predominantly tender joints than those with predominantly swollen joints at 4, 12, and 24 weeks. Indeed, by week 24, the median patient global VAS was 26 versus 8 points and a similar trend was seen for joint pain VAS (23 vs 6 points) and HAQ-DI (0.75 vs 0.13 points). Tender joint counts significantly correlated with these measures at all timepoints.
This significant association between tender joint count and PROMS in the absence of an association with objective assessments of inflammation, “may be related to tenderness being caused by factors other than inflammation,” say the researchers who point out that pain catastrophizing is “a critically important variable in understanding the experience of pain in patients with rheumatologic disorders.”
They propose in Rheumatology Advances in Practice that “pain catastrophizing though not examined in our study, may be a potential explanation for the relation between [tender joint count] and PROMs.”
Hammer and co-authors conclude: “[F]urther studies are needed to develop clinical composite scores that more closely reflect the inflammatory activity.”
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