Analytical interference between lactates and ethylene glycol: a case report

Case report: A 44-year-old man was admitted to the emergency department following a loss of consciousness with cardio-respiratory arrest recovered with adrenaline. Facing this clinico-biological state (cardiovascular failure, cerebral edema, lactic acidosis with 17.54 mmol/L of lactates) and given the patient history (type 2 diabetes mellitus on metformin, psychiatric disorders), a toxicology profile was done with ethylene glycol and metformin dosage. Materials and methods: Two methods are carried out to quantify ethylene glycol: the first method by spectrophotometry used only for emergency and the second one by gas chromatography coupled to mass spectrometry (GC-MS) used for confirmation and allows the dosage of 6?other glycols. Plasmatic concentrations of metformin were determined by high performance liquid chromatography (HPLC). Results: Plasmatic concentration of ethylene glycol obtained by spectrophotometry was 84?mg/L on the first blood sample (the first hours of hospitalization) with a limit of quantification of 50?mg/L. On the second blood sample (2nd day of hospitalization), the ethylene glycol concentration was less than 50?mg/L. The determination by GC-MS on the same samples did not find traces of ethylene glycol. The plasmatic concentrations of metformin measured on the 1st and 2nd days of hospitalization were respectively 14.46?mg/L and 0.7?mg/L (therapeutic level < 1.34?mg/L). Conclusion: Conflicting results between GC-MS method and the non-specific spectrophotometric method oriented towards an analytical interference between ethylene glycol and plasmatic lactates for a concentration over 6.25 mmol/L. Consequently, a lactate level should be done before any spectrophotometric dosage of ethylene glycol to assess the risk of analytical interference. ? Cas clinique?: Un homme de 44 ans a ?t? admis aux urgences suite ? une perte de connaissance avec arr?t cardio-respiratoire r?cup?r? sous adr?naline. Devant le tableau clinico-biologique (d?faillance cardiovasculaire, ?d?me c?r?bral, acidose lactique avec lactates ? 17,54 mmol/L) et les ant?c?dents du patient (diab?te trait? par metformine, ant?c?dents psychiatriques), l'origine toxicologique a ?t? explor?e?: dosage de l'?thyl?ne glycol et de la metformine. Mat?riel et m?thodes?: Deux techniques ont ?t? mises ? profit pour doser l'?thyl?ne glycol?: la premi?re, par colorim?trie, r?serv?e ? l'urgence et la deuxi?me, technique de confirmation, par chromatographie gazeuse coupl?e ? la spectrom?trie de masse (GC-MS) qui permet le dosage de 6 autres glycols. La metformine a ?t? dos?e par chromatographie liquide haute performance. R?sultats : La concentration plasmatique de l'?thyl?ne glycol mesur?e par colorim?trie a ?t? de 84?mg/L sur le premier pr?l?vement (r?alis? ? l'arriv?e aux urgences) pour un seuil de quantification ? 50?mg/L. Sur un deuxi?me pr?l?vement (2?mejour d'hospitalisation), la concentration est pass?e en dessous du seuil de quantification. Le dosage par GC-MS sur ces m?mes pr?l?vements n'a pas retrouv? de traces d'?thyl?ne glycol. Les concentrations plasmatiques de metformine mesur?es aux 1eret 2?mejours d'hospitalisation ont ?t? respectivement de 14,46?mg/L et 0,70?mg/L (concentration th?rapeutique?< 1,34?mg/L). Conclusion?: Les r?sultats discordants entre la technique GC-MS et la technique colorim?trique (peu sp?cifique) ont permis de r?v?ler une interf?rence analytique entre l'?thyl?ne glycol et les lactates plasmatiques pour une lactat?mie >?6,25 mmol/L. Pour tout dosage colorim?trique de l'?thyl?ne glycol, un dosage des lactates doit ?tre r?alis? pour ?valuer le risque d'interf?rence analytique.