Effect of heparinization and overnight storage of blood samples on concentration of eosinophil cationic protein in asthmatic children and controls

We investigated the effect of heparinization and overnight storage of blood samples on circulating levels of eosinophil cationic protein (ECP) in asthmatic children and controls. When centrifuged after 1-hour storage at room temperature, the ECP values of both serum and plasma samples with heparin from asthmatic children were higher than those from corresponding controls. ECP values were higher in serum samples than in plasma samples with heparin obtained from asthmatic children (p < .01), although no differences were found between them in controls. After 18-hour storage at room temperature, the ECP values increased significantly in serum samples obtained from asthmatic children (p = .33), as compared with those obtained after 1-hour storage. No difference in ECP values were found between 1-hour and 18-hour storage using plasma samples with heparin from asthmatic children (p = .18), serum samples from controls (p = .15), and plasma samples with heparin from controls (p = .15). The ECP values correlated with circulating eosinophil counts using serum samples after 1-hour (r = 0.67, p = .002) and 18-hour storage (r = 0.45, p = .04), but not with plasma samples with heparin. Our study indicated that in vitro clotting is necessary for adequate ECP release and the blood sample processing methods would be more important in blood samples of asthmatic children with eosinophilia than with controls.