Validation of an EMIT® screening method to detect 6-acetylmorphine in oral fluid

An automated assay was modified and validated to qualitatively screen for 6-acetylmorphine (6-AM) in oral fluid using the Siemens EMIT II(®) Plus 6-AM urine assay. The validation utilized an oral fluid calibrator at the currently proposed Substance Abuse and Mental Health Services Administration cutoff concentration of 4 ng/mL, as well as quality control material prepared and validated through liquid chromatography-tandem mass spectrometry. All calibrator, quality control and unknown specimens were analyzed based on the dilution and buffering system of the Quantisal(®) oral fluid collection device. Immunoassay parameters such as the pipetted sample and reagent volumes as well as photometric read times were adjusted as part of the assay modification process. Validation experiments included the determination of intra- and inter-day precision and reproducibility, limits of detection (LODs), assay selectivity, stability studies and a specimen agreement study (n = 132). The 6-AM assay performed well in all validation experiments, over multiple days and under various laboratory conditions. The LOD was determined to be 1.844 ng/mL. The assay sensitivity, specificity and overall misclassification rate were found to be 90, 100 and 6%, respectively.