Stability of IgE in Postmortem Plasma and Hemolyzed Samples.

ABSTRACT: Objective To investigate the stability of IgE in postmortem plasma and hemolyzed samples under different storage conditions and freezing-thawing. Methods Thirty nine cardiac blood samples were collected from non-frozen corpses with the postmortem interval of less than 48 hours, including 20 plasma samples and 19 hemolyzed samples taken from whole blood. The samples were stored at -20 ℃, 4 ℃ and 25 ℃ for 28 d and at -80 ℃ for 1 year to evaluate the stability of IgE under different storage conditions. Repeated freezing-thawing treatment was conducted for 5 times to explore the stability of IgE in postmortem plasma and hemolyzed samples. IgE concentration in plasma and hemolyzed samples was detected by electroluminescence before and after treatment. Results The degradation rates of IgE in plasma samples under the three storage conditions, -20 ℃, 4 ℃ and 25 ℃ were close. After 28 d, the mean value was about 15%, the degradation speed of IgE in hemolyzed samples was faster than that of plasma under the same condition （P<0.05） and the degradation rate was faster than other two conditions under 25 ℃ （P<0.05）. The differences in the concentration of plasma samples after freezing at -80 ℃ for 1 year and that before freezing had no statistical significance （ P>0.05）, while the concentration of hemolyzed samples was degraded after freezing at -80 ℃ for 1 year （P<0.05）. The differences between the detection results of plasma and hemolyzed samples after repeated freezing-thawing for 5 times and that before freezing-thawing showed no statistical significance （ P>0.05）. Conclusion IgE has good freezing-thawing stability in postmortem plasma and hemolyzed samples. Stability of IgE is better in postmortem plasma samples than hemolyzed samples, thus it is recommended to separate plasma from postmortem blood samples as soon as possible in forensic practice.