Validation of the Neogen ELISA Benzodiazepine Kit using Clonazepam as the Target Molecule for Blood and Urine

Abstract

This study demonstrates the validation of a semi-quantitative method for the rapid screening of whole blood and urine specimens using clonazepam as the target molecule for the Neogen® Benzodiazepine kit. Decision points were validated at 10.0 ng/mL for whole blood and 25.0 ng/mL for urine. The validation design was based on the Scientific Working Group for Forensic Toxicology (SWGTOX) Standard Practices for Method Validation and included the evaluation of sensitivity, precision, specificity, carryover, hook effect, drift, ruggedness/robustness and a case sample evaluation. The experimental limit of detection for clonazepam was determined to be at least 5.0 ng/mL in whole blood and at least 10.0 ng/mL in urine. Excellent precision was demonstrated when the assay was evaluated using the mean of three replicates from five separate runs (n = 15) at the decision point and at concentration levels ±50% and +100% of the decision point. Although the method was optimized and exceptional precision was demonstrated at each level, the current SWGTOX validation requirements for a valid decision point were not fulfilled. However, both the blood and urine matrix did meet the proposed revision of the SWGTOX requirements for determining a valid decision point promulgated by the American Academy of Forensic Sciences Standards Board and the assay was reliably able to detect benzodiazepines without interference from matrix components or other compounds routinely detected in authentic case samples. Case sample results were comparable with those obtained when the samples were initially screened using oxazepam as the target molecule. The Neogen® Benzodiazepine kit using clonazepam as the target molecule exhibited cross-reactivity for 29 different benzodiazepines and demonstrated excellent precision and sensitivity in both whole blood and urine, making it an efficient and reliable method to screen for benzodiazepines, even though the validation did not fulfill current SWGTOX requirements for a valid decision point.