Calprotectin May Predict Arthritis Relapse

Baseline calprotectin serum levels independently predicted disease relapse in patients with rheumatoid arthritis (RA) and psoriatic arthritis (PsA) taking tumor necrosis factor inhibitors (TNFi) therapy, according to a study published online Dec. 13, 2018 in Arthritis Research & Therapy. Predicting relapses could improve care and avoid related costs, the authors say.

Calprotectin, a proinflammatory factor, is a known biomarker of disease activity and predicts relapse in juvenile idiopathic arthritis. The present study analyzed the accuracy of serum calprotectin levels and drug trough serum levels (TSL) to detect subclinical disease activity and predict relapse in RA and PsA patients. Enrolled patients were in remission or had low disease activity while receiving TNFi (March 2013 to September 2014). While 103 patients (47 RA, 56 PsA) enrolled at a single center, only 95 completed one year of follow-up.

Calprotectin serum levels, TNFi trough serum levels, and antidrug antibodies were evaluated at baseline and during disease relapse using an enzyme-linked immunosorbent assay test kit. Additionally, serum samples were collected at 4, 8, and 12 months of follow-up to assess longitudinal changes in drug trough serum levels.

Over the year of follow-up, 12 patients experienced a relapse. While time-to-remission/low disease activity, calprotectin levels and TNFi TSL were significantly associated with disease relapse, only baseline calprotectin levels independently predicted disease relapse. Calprotectin fully predicted relapse (area under the curve, 1.00).  An optimal calprotectin level of 3.7 μg/mL predicted relapse. This calprotectin cut-off level had a sensitivity of 100 percent and a specificity of 98.8 percent for the diagnosis of a relapse with a positive likelihood ratio of 83 and a negative likelihood ratio of 0.

Serum samples were analyzed during relapse and a significant increase in calprotectin levels was seen in 10 of 12 patients, while TNFi trough serum levels decreased in all relapsers compared with baseline values.

"Calprotectin may be used to stratify disease activity more accurately in patients with low disease activity, guiding therapeutic decisions towards safer and more cost-effective strategies," write the authors led by José Inciarte-Mundo, from University of Barcelona in Spain.

Takeaway: Baseline serum levels of calprotectin may identify residual, subclinical inflammatory activity in patients with low RA or PsA disease activity and can serve as a strong predictor of disease relapse.