HNL (Human Neutrophil Lipocalin) and a multimarker approach to the distinction between bacterial and viral infections

Abstract Objectives The distinction between bacterial and viral causes of acute infections is a major clinical challenge. In this report we investigate the diagnostic performance in this regard of nine candidate biomarkers together with HNL (Human Neutrophil Lipocalin). Methods Blood was obtained from patients with symptoms of infectious ( n  = 581). HNL was measured in whole blood (B-HNL) after pre-activation with the neutrophil activator fMLP or in plasma (P-HNL). Azurocidin also known as heparin-binding protein (HBP), Calprotectin, PMN-CD64, CRP (C-reactive protein), IP-10 (Interferon γ-induced Protein 10 kDa), PCT (Procalcitonin), TK1 (Thymidine kinase 1), TRAIL (TNF-related apoptosis-inducing ligand) were measured in plasma/serum. Area under the ROC (receiver operating characteristics) curve (AuROC) was used for the evaluation of the clinical performance of the biomarkers. Results Side-by-side comparisons of the ten biomarkers showed large difference in the AuROC with B-HNL being the superior biomarker (0.91, 95% CI 0.86–0.95) and with the other nine biomarkers varying from AuROC of 0.63–0.79. The combination of B-HNL with IP-10 and/or TRAIL increased the diagnostic performance further to AuROCs of 0.94–0.97. The AuROCs of the combination of CRP with IP-10 and/or TRAIL were significantly lower than combinations with B-HNL 0.87 (95% CI 0.83–0.91). Conclusion The diagnostic performance of whole blood activated HNL was superior in the distinction between bacterial or viral infections. The addition of IP-10 and/or TRAIL to the diagnostic algorithm increased the performance of B-HNL further. The rapid analysis of HNL, reflecting bacterial infections, together with biomarkers reflecting viral infections may be the ideal combination of diagnostic biomarkers of acute infections.