Effect of collection and preprocessing methods on neutrophil elastase plasma concentrations

Area of Science:

• Clinical Chemistry
• Pediatric Critical Care
• Laboratory Medicine

Background:

• Elevated elastase alpha 1-proteinase inhibitor complex (E-alpha 1 PI) is a proposed marker for bacterial infection and neutrophil activation.
• Potential preanalytical interference from elastase liberation post-blood collection necessitates validated methods, especially for neonates and children.

Purpose of the Study:

• To evaluate the impact of preanalytical methods, specifically different blood collection tubes, on E-alpha 1 PI measurements.
• To validate collection methods for critically ill neonates and children, focusing on EDTA tubes.

Main Methods:

• Compared varying acceleration speeds and centrifugation times, establishing 1550 g for 3 min for leukocyte-free plasma.
• Assessed E-alpha 1 PI absorption by different collection tubes.
• Analyzed samples from healthy adults and critically ill neonates/children using a turbidimetric assay.

Main Results:

• One plasma-separation gel tube absorbed 22.1% of E-alpha 1 PI.
• No significant differences in healthy adults across tubes without absorption.
• Critically ill neonates/children showed significantly higher E-alpha 1 PI in plain Li-heparin, EDTA, and citrate tubes compared to Li-hep with cell-plasma separation gel.

Conclusions:

• E-alpha 1 PI results in critically ill neonates and children are dependent on the blood collection tube type.
• Standard collection tube recommendations for adults may not apply to pediatric critical care patients.