For years scientists have been studying potential serologic biomarkers to predict disease activity in rheumatologic conditions. Unfortunately, the vast majority of biomarkers turned out to be essentially useless or impractical in the clinical setting. We have been left with ESR and CRP, neither of which are sensitive nor specific for disease flare.
Calprotectin is a molecule that is found on leukocytes and is released during inflammation. In a study of 103 RA and PsA patients, calprotectin was strongly correlated with DAS28 score whereas no significant correlation was detected for ESR and CRP (abstract #2926).
The RAVE trial investigated calprotectin levels in ANCA-associated vasculitis patients (abstract #1860). Baseline calprotectin levels in patients who had severe and active vasculitis were similar for relapsers and non-relapsers. However, time to relapse was significantly shorter in patients who had smaller decreases in calprotectin levels after 2 months of treatment. Failure to suppress calprotectin was a stronger marker of relapse in ANCA-positive patients. This study did not report on whether calprotectin had any predictive value above ESR and CRP.
These studies show promise for calprotectin as a biomarker for disease activity; however, prospective studies with longer follow-up are needed to confirm these early findings.