Diagnostic potential of neutrophil elastase inhibitor complex in the routine care of critically ill newborn infants

Abstract

It has been suggested that determination of the neutrophil elastase α1-proteinase inhibitor complex (E-α1PI) improves the diagnosis of bacterial infection in newborns. We evaluated the use of E-α1PI measurements in 143 newborns, consecutively admitted to a tertiary intensive care unit, employing a new random access assay and a sampling procedure that minimises post-collection artefacts. The 95% range for non-infected newborns was 20–110 μg/l up to the 5th day of life and 20–85 μg/l thereafter. The sensitivity as to the diagnosis of culture-proven bloodstream infection was 80% for E-α1PI, 86% for the immature to total neutrophil ratio, 64% for C-reactive protein and 37% for the total white blood cell count. The corresponding specificity amounted to 97%, 85%, 85% and 86%, respectively. E-α1PI increases preceded elevations of C-reactive protein by 18 h. Like C-reactive protein, E-α1PI levels did not distinguish between bloodstream infection and non-bacterial inflammatory responses. Results of E-α1PI became available within 1 h of collection and usually 2–3 h before manual leucocyte counts.

Conclusion Determination of neutrophil elastase α1-proteinase inhibitor levels yields diagnostic advantages comparable to those of manual differential counts but provide faster turnaround times.