[Accreditation of the toxicological screening: recommendations of the SFBC-SFTA group]. / Accréditation du criblage toxicologique : recommandations du groupe SFBC-SFTA.

Toxicological screening is a specific approach to analytical toxicology that uses analytical tools such as GC-MS, LC-UV (diode array) or LC-MS. Toxicological screening allows the detection and simultaneous identification of a large number of compounds. The results may be based on the use of one or more techniques. As part of the accreditation process for medical biology examinations according to standard NF EN ISO 15189, the group from SFTA and SFBC recommends an approach to accredit toxicological screening. Indeed, the complexity of the accreditation of this analysis comes in particular from the high number of compounds that can be detected. Validation parameters are discussed in the specific context of toxicological screening by considering two distinct approaches: the simple identification of compounds, or the identification and estimation of a range of concentration related to clinical outcomes.

A Severe Neonatal Lymphopenia Associated With Administration of Azathioprine to the Mother in a Context of Crohn's Disease.

Azathioprine is commonly used in Crohn's disease. It has been administered to many pregnant women over many years without significant side effects. However, pancytopenia and severe combined immune deficiency-like disease have been reported in infants whose mothers received azathioprine throughout pregnancy. Moreover, myelotoxicity has been described in patients being treated with azathioprine and having a low or absent thiopurine S-methyl transferase [TPMT] activity.Here, we describe the case of a newborn girl found to be highly lymphopenic [< 300 CD3+ T cells] after a positive newborn screening for severe combined immuno deficiency. The clinical examination was normal. The mother was treated with azathioprine throughout her pregnancy, without any reduction of the dose. It was shown that the mother was heterozygous for the 3A [TPMT] activity mutation and that the baby was homozygous for the same mutation; 6-thioguanine nucleotides were high (744 pmol/8.108 red blood cells [RBC]) in the mother and detectable in the infant [177 pmol/8.108 RBC].Although rare, this case illustrates the potential grave consequences of unsuspected TPMT homozygosity in a newborn of a mother receiving thiopurines during pregnancy. Because of the severity of the risk for the newborn, consideration should be given to performing maternal genetic testing and newborn routine blood count in cases of thiopurine treatment during pregnancy.

Evaluation of a Methotrexate Chemiluminescent Microparticle Immunoassay: Comparison to Fluorescence Polarization Immunoassay and Liquid Chromatography-Tandem Mass Spectrometry.

OBJECTIVES: For most laboratories, methotrexate (MTX) concentrations are routinely monitored by fluorescence polarization immunoassay (FPIA). In anticipation of an announced withdrawal of the FPIA reagent on the Abbott TDxFLx (Abbott Diagnostics, Abbott Park, IL), we have evaluated a new reagent kit developed by Abbott on the Architect i1000, based on chemiluminescent microparticle immunoassay (CMIA). METHODS: Precision, inaccuracy, and selectivity were assessed. Interassay variability was established using 75 plasma patient samples treated with MTX and analyzed by two methods: FPIA and liquid chromatography-tandem mass spectrometry (LC-MS/MS). RESULTS FOR MTX,: the intraday inaccuracy was between -6.37% and +3.52%, while interday performance was between -3.70% and 7.90%. Intraday and interday imprecision was less than 2.65% and less than 2.22%, respectively. The correlation coefficient between CMIA and FPIA or LC-MS/MS was 0.9969 and 0.9985, respectively. CONCLUSIONS: These results comparing CMIA vs FPIA and LC-MS/MS indicate that CMIA is a suitable alternative to the FPIA method.