Circulating calprotectin as a supporting inflammatory marker in discriminating SARS-CoV-2 infection: an observational study

Abstract

Objective and design: Fecal calprotectin (CLP) is widely known for its detection in stools of patients with inflammatory bowel diseases (IBDs), to investigate the intestinal inflammatory status. Current research is promoting the circulating protein role as a systemic inflammatory marker. However, most studies report serum calprotectin analysis although plasma assay prevents its massive release by granulocytes. In this perspective, the ongoing SARS-CoV-2 pandemic deserves deployment of convenient and easy-to-dose markers that could reliably address the state of infection.

Methods: We analyzed serum circulating calprotectin (cCLP) levels in hospitalized COVID-19 patients and plasma cCLP levels from patients with suspected SARS-CoV-2 infection, then assessed negative or positive on molecular tests.

Results: Our results confirm a significant circulating calprotectin increase in infected subjects respect to controls, in serum and plasma. Moreover, plasma calprotectin has higher levels in suspected patients with positive SARS-CoV-2-RT-PCR, compared to suspected patients with negative SARS-CoV-2-RT-PCR. Furthermore, ROC curves results showed the circulating plasma calprotectin discriminatory ability to differentiate infected SARS-CoV-2 patients at a cutoff value greater than 131.3 ng/ml.

Conclusions: Our data propose circulating calprotectin as a new, quantitative and predictive marker, which in addition to being an interesting generic inflammatory marker may provide important indications in SARS-CoV-2 infection.

Keywords: COVID-19; Circulating calprotectin; Inflammatory marker; Laboratory medicine; SARS-CoV-2.

Fig. 1

Serum calprotectin concentrations in the negative SARS-CoV-2 RT-PCR control group and in the positive SARS-CoV-2 RT-PCR hospitalized COVID-19 patient group

Fig. 2

Plasma calprotectin concentrations in the healthy negative control group, in the negative SARS-CoV-2 RT-PCR patient group and in the positive SARS-CoV-2 RT-PCR patient group

Fig. 3

Plasma calprotectin ROC curves. Panel A shows the comparison between healthy negative control group and negative SARS-CoV-2 RT-PCR patient group (AUC = 0.8872, p < 0.0001); panel B shows the comparison between healthy negative control group and positive SARS-CoV-2 RT-PCR patient group (AUC = 0.9684, p < 0.0001); panel C shows the comparison between negative SARS-CoV-2 RT-PCR patient group and positive SARS-CoV-2 RT-PCR patient group (AUC = 0.7257, p < 0.0001)