medwireNews: Serum calprotectin levels could represent a useful biomarker of inflammation in people with rheumatoid arthritis (RA) treated with the interleukin (IL)-6 receptor inhibitor tocilizumab, research suggests.
Michael Gernert (University Hospital of Würzburg, Germany) and team explain that measuring inflammation can be particularly difficult in this patient population because “standard inflammation parameters, like erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP), are influenced by interleukin-6-receptor inhibition.”
They therefore evaluated whether calprotectin – previously shown to be a useful marker of inflammation in other immune-mediated diseases – correlated with disease activity in 69 patients with RA from a single center who had been taking tocilizumab for at least 3 months.
The team categorized the tocilizumab-treated participants into those who escalated or switched their DMARDs due to inflammatory activity (active RA) and those who remained on the same treatment with tocilizumab plus concomitant DMARDs during the study (non-active RA), and a total of 125 serum calprotectin measures were taken.
Overall, median serum levels of calprotectin were significantly higher among individuals with active RA than in those with non-active RA, at 4155.5 versus 1040.0 ng/mL. Receiver operating characteristic curve analysis demonstrated that calprotectin, at a cutoff of 1916.5 ng/mL, correctly distinguished between people with active and non-active RA on 84.1% of occasions.
Calprotectin levels also “showed a weak but significant correlation with CDAI values,” with a correlation coefficient of 0.228, write the researchers in Arthritis Research & Therapy.
On the other hand, they found that ESR and CRP levels were not significantly associated with disease activity, whether measured according to CDAI or the requirement for treatment escalation.
These findings indicate that “[c]alprotectin in the serum can be a useful inflammation parameter despite [tocilizumab]-treatment,” say Gernert et al.
They also investigated whether calprotectin was indicative of disease activity in a cohort of 45 RA patients treated with tumor necrosis factor (TNF) inhibitors for at least 3 months. Similar to the findings in the tocilizumab group, TNF inhibitor-treated individuals with active RA had significantly higher serum calprotectin levels than their counterparts with non-active RA (median 5422.0 vs 1845.0 ng/mL). Calprotectin at a threshold of 3690.5 ng/mL had 90.9% accuracy for distinguishing TNF inhibitor-treated patients with active RA from those with non-active RA.
In contrast to the observations in tocilizumab-treated patients, levels of ESR and CRP were significantly higher in TNF inhibitor-treated patients with active versus non-active RA.
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Arthritis Res Ther 2022; 24: 200