Comparing the effect of isotopically labeled or structural analog internal standards on the performance of a LC-MS/MS method to determine ciclosporin A, everolimus, sirolimus and tacrolimus in whole blood.

Background: Liquid chromatography-tandem mass spectrometry (LC-MS/MS) is routinely used for analysis of immunosuppressive drugs. This study investigated whether replacing analog internal standards (ANISs) with isotopically labeled internal standards (ILISs) has an impact on the performance of a LC-MS/MS method for the quantification of tacrolimus (TAC), sirolimus (SIR), ciclosporin A (CsA) and everolimus (EVE) in whole blood.

Methods: Following hemolysis, protein precipitation, and extraction with either ANISs (ascomycin, desmethoxy-rapamycin, CsD), or ILISs (TAC-13C,D2; SIR-13C,D3; CsA-D12; EVE-D4), samples were centrifuged and injected into a LC-MS/MS device equipped with a C18 reversed phase column.

First-trimester screening biochemical markers (free beta-subunit human chorionic gonadotropin, pregnancy-associated plasma protein-A) and risk of early fetal loss.

Aim: The aim of this work was to assess the risk of early fetal loss (first trimester of pregnancy, 8-13 weeks of gestation) using the results of first-trimester screening (FTS) biochemical markers independently and combined.

Methods: FTS results of 152 women who suffered early fetal loss were compared to a control group of 150 women with normal pregnancy outcomes. FTS biochemical markers were measured with a Delfia Xpress 6000 analyzer and biochemical risks for Down's and Edward's syndromes were calculated using Prenatal-Lifecycle version 3.