Evaluation of an enzyme immunoassay for the detection of methadone metabolite EDDP [2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine] in urine.

Background: We evaluated a new EDDP [2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine] enzyme immunoassay (EDDPI; Lin-Zhi International, Inc., Sunnyvale, CA) for the detection of this primary methadone urinary metabolite.
Methods: All specimens were tested with two different cutoff calibrators at 150 and 300 ng/ml EDDP on an ADVIA 1200 Chemistry System auto-analyzer. Controls containing 0, -25% (negative control), and +25% (positive control) of the cutoff calibrators (Lin-Zhi) were analyzed with each batch. All urine specimens were then analyzed by high-pressure liquid chromatography/ mass spectrometry/mass spectrometry (HPLC-MS/MS) for EDDP.
Results: Approximately, 42% (151) of the 362 specimens yielded positive results by the EDDP assay at 150 and/or 300 ng/ml cutoff values. Of these specimens, HPLC-MS/MS confirmed the presence of EDDP > 25 ng/ml in all 151 specimens. No specimen yielding negative EDDPI results contained EDDP by HPLC/MS/MS. At 150 ng/ml cutoff, the EDDPI demonstrated a sensitivity of 1.00, a specificity of 0.986, and an overall agreement of HPLC/MS/MS of >99%. At 300 ng/ml cutoff, the EDDPI demonstrated a sensitivity of 1.00, a specificity of 0.959, and an overall agreement of HPLC/MS/MS results of 97.5%.
Conclusion: The Lin-Zhi EDDPI provides a precise, reliable method for the routine detection of methadone metabolite in urine specimens, particularly in pain management compliance testing.
(© 2014 Wiley Periodicals, Inc.)