Application of the Abbott TDx Lidocaine, Phenytoin, and Phenobarbital Assays to Postmortem Blood Specimens

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Abstract
The TDx fluorescence polarization immunoassays (FPIA) for some therapeutically monitored drugs (lidocaine, phenytoin, phenobarbital) were applied to the analysis of postmortem blood specimens. After an initial calibration using the appropriate TDx calibrators, blood bank blood fortified with known amounts of drug was analyzed by FPIA. Postmortem blood specimens containing the drugs, postmortem specimens not containing the drugs of interest (negatives), and randomly selected postmortem blood specimens fortified with known amounts of the drugs were analyzed by the FPIA and reference gas chromatographic (GC) methods. Concentrations determined in blood bank and postmortem blood specimens showed excellent correlation between the two methods and produced lines with slopes ranging from 0.98 to 1.08. In each case the correlation coefficient was greater than 0.97. Analysis of all negative specimens produced FPIA values below the limit of quantitation of the reference GC assay.