Radioimmunoassay Screening and GC/MS Confirmation of Whole Blood Samples for Drugs of Abuse

From 1981 to 1984, an average of 300 radioimmunoassay screens on whole blood were performed each week in the authors' laboratory. Most samples were screened for opiates, phencyclidine and its analogs, barbiturates, and cocaine or its metabolite benzoylecgonine. A commercially available radioimmunoassay was used with modifications to facilitate screening of whole blood. Increasing sample size increased the sensitivity of the assay. Changing reagent concentration (1:1 dilution), incubation time, sample matrix (water, urine, or blood), or fraction counted (precipitate or supernatant) did not affect the utility of the standard curve or the sensitivity of the assay. All positive results for phencyclidine, opiates, cocaine, and related compounds were confirmed by GC/MS. Barbiturate positives were confirmed by UV spectrophotometry. The rate of confirmation in postmortem bloods from coroner's cases for 1981-84 was: cocaine/benzoylecgonine, 57%; opiates, 79%; phencyclidine, 49%; and barbiturates, 58%.