Detection of opiate use in a methadone maintenance treatment population with the CEDIA® 6-acetylmorphine and CEDIA DAU opiate assays

Heroin, with a plasma half-life of approximately 5 min, is rapidly metabolized to 6-acetylmorphine (6-AM). 6-AM, a specific marker for heroin use, which also has a short half-life of only 0.6 h, is detected in urine for only a few hours after heroin exposure. Ingestion of poppy seeds and/or licit opiate analgesics can produce positive urine opiate tests. This has complicated the interpretation of positive opiate results and contributed to the decision to raise opiate cutoff concentrations and to require 6-AM confirmation in federally mandated workplace drug-testing programs. Microgenics Corp. has developed the CEDIA 6-AM assay, a homogeneous enzyme immunoassay for semiquantitative determination of 6-AM in human urine, in addition to its CEDIA DAU opiate assay. Urine specimens were collected 3 times per week from 27 participants enrolled in a clinical research trial evaluating a contingency management treatment program for heroin and cocaine abuse. Of the 1377 urine specimens screened, 261 (18.9%) were positive for opiates at ≥300 ng/mL, 153 (11.1%) were positive for opiates at ≥2000 ng/mL, and 55 (4.0%) were positive for 6-AM at ≥10 ng/mL. For opiate-positive screens ≥300 and ≥2000 ng/mL, 91.3% and 80.8% confirmed positive for morphine or codeine at the respective gas chromatography-mass spectrometry (GC-MS) cutoffs. All specimens screening positive for 6-AM also confirmed positive by GC-MS at ≥10 ng/mL. Increasing the opiate screening and confirmation cutoffs for the federal workplace drug-testing program resulted in 8% fewer opiate-positive tests; however, recent heroin use was not affected by this change.