Immunchemisches Screening von Serumproben: Vergleich der Cannabinoid- und Opiat-Assays Mahsan MTP und Abbott FPIA mit Kontrolle durch Gaschromatographie-Massenspektrometrie

By the update of §24?a of the German road traffic act driving under the influence of drugs of abuse can now be fined even in ¶absence of an actual driving impairment. ¶The only requisite is the detection of certain drugs/metabolites in a blood sample. Therefore for pretesting there is a need for fast and reliable immunological screening methods in blood/serum. The new Mahsan microtiterplate enzyme immunoassay (MTP-EIA) is claimed to be sensitive and independent of the matrix. For an evaluation we carried out a comparison of the cannabinoid and opiate assays from Mahsan (MTP-EIA) and the routinely used Abbott fluorescence polarization immunoassay (FPIA) with a batch of routine serum samples. For the MTP-EIAs we used the cut-off recommendations of the supplier (cannabinoids 2 ng/mL, opiates 10 ng/mL). For the Abbott FPIAs the serum samples had to be pretreated (deproteinization with acetone) and appropriate cut-offs were defined by our investigations (cannabinoids 20 ng/mL, opiates 30 ng/mL). Out of 136 samples screened for cannabinoids 42% were positive with GC-MS and 18% from 123 samples were positive for opiates. The Abbott cannabinoid FPIA gave false negative results in 23% of GC-MS positive cases and 9% false negatives for opiates while Mahsan MTP-EIA gave no false negatives. Each of the two cannabinoid assays gave false positive results in 13% of the cases and for the MTP opiate assay 2% of the positives could not be confirmed with GC-MS. As a result of our study the cut-off values for the MTP-EIAs have proved to be suitable for a distinction between potential positives and true negatives.