Calprotectin Fecal Assay Adapted for Serum Samples

Calprotectin is a calcium-binding protein that belongs to the S100 family, which is present in immune cells such as macrophages, monocytes, and neutrophils and in epithelial and endothelial cells. Increased serum and plasma calprotectin concentrations have been found in chronic inflammatory rheumatic disorders.

Calprotectin can be measured in serum, plasma, and feces. Increased serum and plasma calprotectin concentrations have been found in chronic inflammatory rheumatic disorders such as juvenile chronic arthritis, rheumatoid arthritis (RA), Behçet disease, and Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis.

Image: The LIAISON XL is a fully automated chemiluminescence analyzer, performing complete sample processing as well as measurement and evaluation (Photo courtesy of Medical Laboratory Observer)

Clinical Biochemists at the Hospital Clinic of Barcelona (Barcelona, Spain) evaluated the association between calprotectin serum levels and disease activity in RA, they included 49 consecutive patients with RA (fulfilling ACR/EULAR 2010 classification criteria) evaluated during the course of 2019 in the outpatient clinic of Rheumatology of their hospital, with different degrees of disease activity. Serum calprotectin concentrations in 26 active and 23 remission RA patients were compared.

The scientists used the LIAISON® XL (DiaSorin, Saluggia, Italy) for the quantitation of serum calprotectin. This is a fully automated analyzer using chemiluminescence technology with magnetic microparticles that performs complete sample processing, as well as measurement and evaluation being able to analyze up to 180 tests per hour. Forty-two serum samples in the range from 0.5 to 10 µg/mL were analyzed using DiaSorin Liaison Calprotectin assay and CalproLab ELISA kit (Svar, Malmö, Sweden), a validated assay for testing plasma/serum samples.

The investigators reported that the intra-day and inter-day analytical imprecision CVs ranged from 2.9% to 4.0% and 2.7% to 10.4%, respectively. Correlation between measured and expected values was high indicating good linearity. The Wilcoxon signed-rank test showed that serum and plasma matched samples presented statistically significant differences, where the highest concentrations of calprotectin observed in serum samples. Significantly higher serum calprotectin levels were found in RA patients with active disease when compared to patients with low disease activity or in clinical remission (mean ± SD) [(3.35 μg/mL ± 1.55) versus (1.63 μg/mL ± 0.52), and these levels correlated well with all disease activity indices.

The authors concluded that the DiaSorin Liaison fecal Calprotectin assay adapted for serum samples showed adequate technical performances and a good agreement with CalproLab ELISA kit, furthermore, the clinical performances are similar to other assays. They have estimated reference limits in patients with RA and observed a good correlation between serum calprotectin and RA activity, similar to those reported previously. The study was published on February 5 2022, in the Journal of Clinical Laboratory Analysis.

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Hospital Clinic of Barcelona 
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