Evaluation of a rapid bedside toxicology screen in patients suspected of drug toxicity.

Although rapid bedside toxicological screening is reliable, it has not been validated in the emergency department (ED) setting. We assessed the accuracy of a 10-min bedside immunoassay, Triage Panel (TP), for 7 drugs of abuse and tricyclic antidepressants (TCA) in ED patients suspected of drug toxicity. This was a prospective observational study conducted at an urban teaching ED (100,000 visits/year) of patients suspected of drug toxicity during a 7-month period. The assay was compared for agreement with combined SYVA EMIT and TLC. GC/MS or HPLC was used for analyzing sensitivity and specificity in discordant findings. A total of 172 cases (ages 0.6-73 years) were screened with TP, and 100 (58%) were found to be positive for at least one drug. Sensitivity (proportion and 95% CI) was as follows: cocaine 30/31 (90.6-100%), phencyclidine no cases, THC 21/24 (80.1-94.3), opiates 14/14 (100), amphetamines 1/1 (NA), barbiturates 10/10 (100), benzodiazepines 20/21 (90.5-99.9), and TCA 13/13 (100). Specificity was above 98% for every drug except TCAs (which was 95%), partly due to interference from iminostilbene (a carbamazepine metabolite) in three cases. Agreement between TP and hospital laboratory was over 90% for every drug class. Both benzodiazepines and THC showed significant disagreement between the two testing modalities. In conclusion, in a series of ED patients suspected of drug toxicity, the TP was an accurate tool to rule out the presence of seven drugs of abuse and TCAs. Further testing will be required to verify the efficacy of the test in populations with a higher prevalence of phencyclidine and amphetamine abuse.