Serum measurements of human neutrophil lipocalin (HNL) discriminate between acute bacterial and viral infections

Abstract

Human neutrophil lipocalin (HNL) is a recently identified protein from human neutrophil granules. The concentrations of HNL in the circulation were measured, in a group of patients with acute infections, using a radioimmunoassay. The concentrations of HNL in patients infected by viruses and bacteria were 93.78±45.30 μg 1^-1 (SD), 404.14±355.02 μg 1^-1 (SD) in serum, and 47.81±18.18 μg 1^-1 (SD), 145.46±194.32 μg 1^-1 (SD) in plasma, respectively. The differences between the two patient groups were highly significant. There was a significant correlation between serum HNL and plasma HNL levels in bacterial infections (r = 0.73, p<0.0001). The HNL serum levels also correlated with those of C-reactive protein (CRP) (r = 0.59, p<0.0001). Determination of HNL in serum was more specific and sensitive than CRP in the distinction between viral and bacterial infections. At a cut-off of 155 μg 1^-1 (HNL in serum), the positive and negative predictive values for the diagnosis of bacterial infections were 92 and 96%, respectively, which were superior to the optimal predictive values of CRP. Thus, the determination of HNL level is useful in the diagnosis of acute bacterial infections.

Key Words:

• C-reactive protein
• diagnosis
• predictive value
• radioimmunoassay
• sensitivity
• specificity