Lack of Detection of New Amphetamine-Like Drugs Using Conventional Urinary Immunoassays

The number of reports of serious adverse effects and intoxication after the use of the new drug 4-fluoroamphetamine (4-FA) increases. At the Emergency Department of the OLVG-Oost Hospital in Amsterdam, an on-site drug test, the Triage TOX Drug Screen, is available to assist in a rapid diagnosis. In less urgent cases, an EMIT II Plus immunoassay is used to determine semiquantitatively the presence of drugs of abuse (DOA). The antibodies in these immunoassays are designed to detect classic DOA and its urinary metabolites. Amphetamine-like drugs that may cause serious toxicity or impairment may not cross-react with the available immunoassay kits, and therefore may stay undetected. The question arises as to whether 4-FA and paramethoxymethamphetamine (PMMA) are detectable in the toxicological screening procedures commonly used for testing in urine.

Synthetic urine was spiked with the drug under investigation to create spiking standards of 50, 100, 250, 500, 2500, and 5000 ng/mL. Urine drug screens were performed on the automated analyzer Biosite Triage MeterPro using the Triage TOX Drug Screen test and on a Siemens Drug Testing System Viva-E using the EMIT II Plus Ecstasy Assay and the EMIT II Plus Amphetamines Assay.

In this concentration range, the EMIT II Plus did not screen positive for PMMA, but there was some cross-reactivity for PMMA on the EMIT II Plus Ecstasy assay. The Triage TOX Drug Screen did test positive for PMMA at a concentration of 2500 ng/mL. The EMIT II Plus Amphetamines did test positive for 4-FA at a concentration of 5000 ng/mL, whereas the Ecstasy [3,4-methylenedioxymethamphetamine (MDMA)] assay only showed low cross-reactivity for 4-FA. The Triage TOX Drug Screen did not test positive for 4-FA.

The available immunoassays lack sensitivity to detect 4-FA and PMMA in lower urine concentrations. Awareness of the fact that novel DOA may lead to false-negative urinary drug tests is of great importance.