Determination of total interleukin-8 in whole blood after cell lysis

Background: It has been shown that a high percentage of interleukin-8 (IL-8 ) in blood is cell associated. Recently, a simple method for determination of cell-associated IL-g in whole blood after cell lysis has been dec-scribe d. The purpose of this study was to evaluate this method, to examine the in fluence of preanalytic sample handling, and to establish the concentration range of total IL-8 and its relation to age and sex in healthy subjects. Methods: Total IL-8 content of whole blood was determined after lysing bloo d cells with Milenia(R) cell lysis solution. IL-8 in the resulting blood ly sate was measured with the IMMULITE(R) IL-8 immunoassay. Results: When freshly drawn blood was stored up to 48 h on ice, no signific ant changes in total IL-8 were measured in the subsequently prepared lysate , whereas with storage at room temperature, total IL-8 increased after 3 h from 94 +/- 13 ng/L, to 114 +/- 16 ng/L (n = 10). In lysate stored for 48 h at 4 degrees C marginal changes of the IL-8 concentration were noted, with storage at room temperature, only 76% +/- 5% (n = 12) of initial concentra tion was recovered. From lysate frozen at -20 and -80 degrees C, respective ly, 84% +/- 4% and 93% +/- 2% of initial IL-8 was recovered after 70 days ( n = 10). IL-8 was measured with comparable precision in plasma (CV, 3.2-4.2 %) and blood lysate (CV, 3.7-4.1%). When plasma was diluted with cell lysis solution, a slightly overestimated recovery (125% +/- 3%) was observed; fo r lysate specimens with a cell lysis solution content greater than or equal to 75%, the recovery after dilution was 98% +/- 2%. In lysate prepared fro m 12 blood samples with exogenous IL-8 added, IL-8 recovery was 104% +/- 2% (recovery from plasma <35%). The median total IL-8 in blood lysates from 1 03 healthy subjects (22-61 years) was 83 ng/L of blood (2.5-97.5 percentile range, 49-202 ng/L of blood). In females but not in males, total IL-8 incr eased significantly with advancing age (P <0.002). We found grossly increas ed total IL-8 in six pregnant women with amniotic infection syndrome. Conclusions: The evaluated method allows the assessment of total IL-8 in bl ood with good performance when appropriate conditions of sample pretreatmen t are considered. The values in healthy volunteers all were above the detec tion limit of the IL-8 assay; therefore, slight changes of total IL-8 could be noted. Thus, the present method is a suitable tool to study the diagnos tic relevance of total IL-8 in blood. (C) 2000 American Association for Cli nical Chemistry.