[Treatment of Dravet disease and false urine testing with ecstasy: a little-known interference]

Urine drug screening is carried out on numerous automated analysis platforms using enzyme-linked immunosorbent assays. While these methods are rapid, they often lack specificity. We report the case of a 5-year-old child treated for Dravet disease and hospitalized for clonic seizures. During her hospitalization, 3 urine samples were sent to the Toxicology laboratory to rule out any toxic origin to these seizures. The first two were positive for ecstasy, and negative for other drugs. For the last sample, all tests were negative. The presence of ecstasy in the first 2 samples was not confirmed by gas chromatography-mass spectrometry, which identified stiripentol in all 3 urines. Stiripentol is an antiepileptic drug that shares a 3,4-methylenedioxy group with MDMA. We determined that the antibody in the kit crossed 20% with stiripentol, and were able to define a stiripentol cut-off concentration of 2,500 ng/mL. We checked this cut-off by measuring stiripentol in the 3 urine samples, finding concentrations of 47,600 and 5,800 ng/mL for the first and second samples respectively, and 1,900 ng/mL for the last. These concentrations explain the false positives in the first two urine samples, and the negative result in the last. This work underlines the need to remain critical of the results of immuno-screening methods, and to confirm them with a reference method.