COMPARISON OF SERUM AND PLASMA LEUKOTRIENE B-4 LEVELS IN NORMAL AND ASTHMATIC SUBJECTS

Background: Leukotriene B-4 (LTB(4)) serum and plasma concentrations w ere reported to be higher in some asthmatic patients than in normal su bjects; however, reported LTB(4) concentrations in normal subjects var y widely. One study suggested that blood clotting causes the increased LTB(4) concentration. Objective: To determine whether LTB(4) concentr ation is increased in asthmatic patients, and whether it is affected b y clotting. Methods: We studied seven normal subjects and nine clinica lly stable asthmatic patients. Venous blood was drawn into test tubes without additives; containing heparin; or containing heparin and cyclo - and lipoxygenase inhibitors. Cells were separated after 30 minutes. Leukotriene B-4 was measured by radioimmunoassay following its extract ion from serum or plasma. In three subjects, plasma was separated also at times 0 through 30 minutes. Results: Serum and plasma concentratio ns of LTB(4) in normal volunteers and asthmatic patients were similar, but the variance of LTB(4) concentrations among the asthmatic patient s was significantly higher than in the normal subjects, Leukotriene B- 4 concentrations, measured in plasma only, were significantly reduced in both asthmatic and nonasthmatic subjects in the presence of inhibit ors. There was no significant difference in LTB(4) concentrations betw een time 0 and 30 minutes, but there was considerable variability. Con clusions: We conclude that clotting is unlikely to affect serum LTB(4) concentrations. Leukotriene B-4 serum and plasma concentrations are n ot consistently increased in asthmatic patients; however, LTB(4) is sy nthesized during and possibly after blood has been drawn. Proper handl ing of the specimens and probably the addition of cyclo-oxygenase and lipoxygenase inhibitors is of the utmost importance for accurate LTB(4 ) determination.