Assessment of the EMIT-(TM) technique as a screening test for opiates and methadone for a methadone maintenance clinic and its calibration by Bayesian statistics.
The performance of the semi-quantitative enzyme multiplied immunoassay technique (EMIT, Syva Corp.) for opiates and methadone has been examined as a screening procedure of urine samples from a methadone maintenance programme. The predictive value model that is based upon Bayesian statistics was used to determine screening levels for the EMIT assays. 2. With a predictive value of a negative result of 100%, the EMIT opiate assay can be used to show the absence of the indicated drugs, while positive results can be confirmed by a non-immunological technique. A screening level of 1.0 micrograms/ml for the opiate assay, conforms to this model. 3. The EMIT methadone assay was shown to have a predictive value of a negative result of 28% with respect to thin-layer chromatographic (TLC) results. This discrepancy between EMIT and TLC can not be explained by sensitivity alone. The manufacturer's recommended 0.5 micrograms/ml cutoff has been used therefore for the methadone assay.
