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Abstract

Whole Blood Interleukin-8 Concentrations in Capillary and Cord Blood of Neonates for the Diagnosis of Systemic Inflammatory States by Klaus P. Kohse, Angelika Carl, Gerald Steinbach

An assay is described for the determination of interleukin 8 (IL-8) in whole blood lysate instead of plasma or serum. EDTA-anticoagulated umbilical cord blood or capillary blood was added to a detergent-containing lysing reagent. This sample was used directly for determination of IL-8 using the Immulite® IL-8 assay kit (DPC, Bad Nauheim, Germany) and the Immulite® Analyzer. Linearity was confîrmed for cord blood as well as for venous blood, at a whole blood to lysing agent ratio from 1:20 to 1:1. IL-8 was stable in whole blood hemolysate at 4°C for at least 3 days; thereafter, concentrations decreased remarkably to 32% of the initial concentration after 8 days. Storage of whole blood prior to hemolysis Ied to increases in IL-8 concentrations of up to 4fold the original values. The intra-assay CV was 3.4% (at 234 ng/L) and 7.4% (at 1080 ng/L) using hemolysate samples. Inter-assay CVs of 13.3% (at 108 ng/L) and 11.7% (at 506 ng/L) were found using control material. Concentrations of IL-8 in whole blood were significantly higher than in the corresponding plasma. ln 70% of 135 apparently healthy neonates' cord blood samples, plasma IL-8 concentrations were below the detection limit of the assay (5 ng/L), whereas a range of 69 - 3150 ng/L IL-8 (median, 266 ng/L) was found in the hemolysate samples of these neonates. A preliminary reference range for IL-8 in whole blood may be set at 132 to 820 ng/L (5th and 95th percentile). In 78 neonates, IL-8 concentrations in hemolysate from capillary blood ranged from 120 ng/L to 2000 ng/L (median, 416 ng/L). The fact that concentrations of IL-8 can be determined using only a very small sample volume (10 µl of whole blood) makes the assay format especially suitable for use in neonatal intensive care. (Clin. Lab. 2002;48:497-503)

DOI: Clin Lab. 2002;48:497-503