Claire Reid

Comparison of GC-MS and EIA Results for the Analysis of Methadone in Oral Fluid

The purpose of these studies was to evaluate the performance characteristics of the Cozart Microplate Enzyme Immunoassay (EIA) for the determination of methadone in oral fluid from patients in a drug misuse treatment program. Oral fluid specimens were collected using the Cozart RapiScan Collection system from 198 donors who were receiving treatment for their addiction and were monitored for drug misuse. Oral fluid specimens were also collected from forty volunteer donors who were not drug users. The specimens were analyzed in the laboratory by EIA and then analysed for methadone and its main metabolite EDDP by gas chromatography-mass spectrometry (GC-MS). A total of 103 samples were confirmed positive for methadone. The Cozart Microplate EIA for d-Methadone in oral fluid using a cutoff of 30 ng/mL in diluted oral fluid had a sensitivity of 91.3% +/- 2.8% and a specificity of 100% +/- 1.0% vs. GC-MS.

Sensitivity and Specificity of the Cozart Microplate EIA Cocaine Oral Fluid at Proposed Screening and Confirmation Cutoffs

BACKGROUND Oral fluid is currently being evaluated as an alternative matrix for monitoring illicit drugs in federally mandated workplace drug testing, for addiction treatment programs, and for driving under the influence testing. The sensitivity, specificity, and efficiency of the Cozart Microplate EIA Cocaine Oral Fluid Kit (COC ELISA) were determined by comparison with gas chromatography-mass spectrometry (GC/MS) results at screening and confirmation cutoffs proposed in the US and UK. METHOD Oral fluid was collected by expectoration after citric acid candy stimulation or with Salivette neutral cotton swabs or Salivette citric acid-treated cotton swabs before and after cocaine (COC) administration. Specimens (n = 1468) were analyzed with the COC ELISA for screening and with solid-phase extraction followed by GC/MS for confirmation. Three screening cutoffs (10, 20, and 30 microg/L) and four GC/MS cutoffs (2.5, 8, 10, and 15 microg/L COC, benzoylecgonine, and/or ecgonine methyl ester) were evaluated. GC/MS limit of quantification was 2.5 micro g/L for all analytes. RESULTS COC ELISA interassay imprecision (CV; n = 19) was 16% at 16.7 microg/L and 12% at 81.8 microg/L. With the 2.5, 8, 10, and 15 microg/L GC/MS cutoffs, 59.0%, 54.7%, 52.7%, and 48.7% of the oral fluid specimens were positive, respectively. Sensitivity, specificity, and efficiency were 92.2%, 84.7%, and 88.8%, respectively, for the suggested Substance Abuse and Mental Health Services Administration (SAMHSA) cutoffs and 90.2%, 89.2%, and 89.7% for cutoffs currently used in the UK. CONCLUSIONS COC ELISA had suitable sensitivity, specificity, and efficiency for identifying COC exposure at both the proposed SAMHSA and UK cutoffs. Sensitivity, specificity, and efficiency were >84% for both cutoffs, but 92 additional true-positive samples were identified with the SAMHSA cutoffs.