From the Journals

Tender joint count may confound assessment of RA inflammation



In RA, patients with predominantly tender joint counts were found to have lower levels of inflammation defined by ultrasound than those with predominantly swollen joints, according to an observational study that has implications for management decisions.

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When patients do not achieve a remission defined by a composite disease activity score (CDAS) that includes tender joint counts, it suggests that inflammation persists, but this may be a “misinterpretation,” according to a report in Arthritis Care & Research by Hilde B. Hammer, MD, PhD, of the department of rheumatology at Diakonhjemmet Hospital, Oslo, and her associates.

In this observational study, 209 RA patients were evaluated at baseline and again at months 1, 2, 3, 6, and 12. The researchers compared 84 patients with predominantly tender joints, defined as tender-swollen joint count difference (TSJD) score of greater than zero, against 125 patients with predominantly swollen joints, defined as TSJD of zero or less.

Scores on specific CDAS measures, such as the Disease Activity Score based on 28 joints, the Clinical Disease Activity Index, and the Simplified Disease Activity Index, were significantly higher (P less than .001) at all visits in patients with predominantly tender joints, compared with those with predominantly swollen joints. Although laboratory markers, such as C-reactive protein and rheumatoid factor, were similar between groups, synovitis as scored with ultrasound assessment was significantly lower (P less than .001) among patients with predominantly tender joints than in those with predominantly swollen joints.

This disparity is important, according to the authors, who suggested that failure to reach a CDAS-defined remission solely on the basis of tender joints might complicate clinical assessment.

“Taking the high impact of CDAS levels in the treat-to-target management of RA into account, our results suggest a careful interpretation of CDAS levels in patients who have predominantly tender joints,” the authors reported.

Based on the evidence from this study, which found tender joints to be a positive predictor of CDAS and patient-reported outcomes but a negative predictor of ultrasound scoring of inflammation, “these results indicate that tender joints do not reflect the same pathology as found with ultrasound,” they wrote.

The research was supported by AbbVie, Pfizer, and Roche in the form of study grants awarded to the department of rheumatology at Diakonhjemmet Hospital via Dr. Hammer and two other authors. Dr. Hammer and the two other authors also reported financial relationships with those companies and others.

SOURCE: Hammer HB et al. Arthritis Care Res. 2018 Nov 26. doi: 10.1002/acr.23815.

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