Comparing ELISA and LC-MS/MS: A Simple, Targeted Postmortem Blood Screen

A comprehensive screening method that is specific, accurate and customizable is necessary in any forensic toxicology laboratory. Most laboratories utilize some form of immunoassay testing as it is reliable and sensitive with minimal sample preparation and is relatively inexpensive to simultaneously screen for multiple classes of drugs with different chemical properties. However, accessibility to more specific technology and instrumentation such as mass spectrometry has increased and therefore using immunoassay as the screening method of choice may be revisited. A screening method for 42 drugs in postmortem blood was developed and validated following the Organization of Scientific Area Committees for Forensic Science guidelines for toxicology method validation. The method was developed using minimal sample preparation of postmortem blood consisting only of a protein precipitation. Only two internal standards were used, which greatly reduces the cost of implementing this method. Limit of detection, interference studies, processed sample stability and ion suppression/enhancement were examined. Additionally, over 100 case samples were analyzed by both the current enzyme-linked immunosorbent assay (ELISA) testing procedure and the proposed liquid chromatography-tandem mass spectrometry (LC-MS/MS) screening method. The comparison determined that the LC-MS/MS method performed as well as or better than the ELISA in nearly all cases. The ability to add additional target drugs increases the laboratory's scope of analysis as well. This method is ideal for forensic laboratories wishing to improve screening while working within budget constraints.