False-Positive Ethanol Level in Urine and Plasma Samples of a Resuscitated Infant

We report the case of an 11-month-old male infant with a complex congenital heart disease who was admitted in the intensive care unit following cardiorespiratory arrest at home. Toxicological urine screening reported an ethanol concentration of 0.65 g/L using an enzymatic assay, without suspicion of alcohol intake; a significant amount of ethanol concentration was found in two plasma samples using the same enzymatic assay. Plasma and urine ethanol concentrations were below the limit of quantification (LOQ) when tested using a gas chromatography method. Urine ethanol level was also below the LOQ when tested by enzymatic assay after an initial urine ultrafiltration. These results confirmed our suspicion of matrix interference due to elevated lactate and lactate dehydrogenase levels interfering in the enzymatic assay. This analytical interference, well-known in postmortem samples, extensively studied in vitro, has been rarely reported in vivo, especially in children. To the best of our knowledge, this case is only the sixth one reported in an infant's plasma and the first initially discovered from urine. Indeed, as for ethanol, this last matrix has not been studied in the context of this artifact that may induce false-positive ethanol results while seeking a diagnosis in life-threatening or fatal situations that are potentially subject to forensic scrutiny. In parallel to a synthetic literature review, we propose a simple, informative decision tree, in order to help health professionals suspecting a false-positive result when performing an ethanol assay.