Soluble mannose receptor levels in blood correlate to disease severity in patients with community-acquired pneumonia.

Purpose: Community-acquired pneumonia (CAP) is the most common form of pneumonia and is a leading infectious cause worldwide. Identification of patients that are at risk to develop severe disease has proven to be a major challenge. Soluble mannose receptor (sMR; sCD206) is a new serum marker for macrophage activation. Recent studies showed that sMR levels are increased in patients suffering from severe infections making it a potential biomarker for improved discrimination of disease severity. For measuring sMR, no standardized assay is available. Aim of this study is to develop an assay for standardized measurement of sMR. Next, this assay was used to assess sMR plasma levels for its ability to predict severe disease development in a patient cohort for community-acquired pneumonia.

Methods: We developed a well-validated sandwich ELISA that enables standardized measurement of sMR in plasma and serum samples. Repeatability was tested by calculating the percentage coefficient of variation (%CV) within and between runs and within and between operators. sMR levels were assessed in a cohort of 100 patients with community-acquired pneumonia.

Results: All %CV values were <10%, indicating low variation. Higher sMR levels were observed in patients with severe disease when compared to patients without severe disease development (p = 0.004). Patients with sMR levels between 100-430 ng/ml had 22.7% chance to develop severe disease whereas patients with levels between 430-1000 ng/ml had 33.3% chance to develop severe disease.

Conclusions: We suggest that sMR has potential as a new biomarker for the prediction of disease severity in patients with community-acquired pneumonia.