| heal.abstract |
Adrenal steroid profiling, including 17 alpha-OH progesterone (17OHP), 11-deoxycortisol (S), androstenedione (Delta 4-A) and cortisol (F) in blood spots by tandem mass spectrometry, is used for newborn screening to detect congenital adrenal hyperplasia (CAH). Pre-analytical sample processing is critical for assay specificity and accuracy; however, it is laborious and time-consuming. This study describes the development and validation of a new Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS) method for the simultaneous quantification of five steroids: 17OHP, S. Delta 4-A, F and cortisone (E) in blood spots from newborns. Whole blood was eluted from a 5.00 mm dried blood spot by an aqueous solution containing the deuterium-labeled internal standards d8-17OHP and d4-cortisol. The steroids extracted from blood spot into aqueous solution were subsequently purified via Extelut mini NT1 column using diethylether. The extracts were evaporated and quantified using LC-MS/MS. The detection limit was 0.25 ng/mL for 17OHP and S, 0.4 ng/mL for Delta 4-A and 0.5 ng/mL for F and E. The limit of quantification was 0.5 ng/mL for 17OHP, S and Delta 4-A and 1 ng/mL for F and E. Precision for 17OHP, S.6, Delta 4-A at concentrations of 0.5, 2, and 8 ng/mL (n = 5) in fortified steroid free serum samples was 1.3-3.5% (intra-assay CV) and 7-14.8% (inter-assay CV). Precision for F and Eat concentrations of 5 and 20 ng/mL was 1.5-4.8% (intra-assay, CV%) and 6-15% (inter-assay, CV%). Accuracy was calculated at concentrations of 0.5, 2, and 8 ng/mL for 17OHP, S and Delta 4-A and ranged from -0.3 to 0.2%, while for F and E it ranged from -3.2 to 0.2%. Relative recoveries at concentration 2 ng/mL and 8 ng/mL for 17OHP, S. Delta 4-A and at 5 ng/mL and 20 ng/mL for F and E ranged from 55% to 80%. Reference intervals were estimated for all steroids in newborns (on day 3). The steroid profile assay herein described is sensitive, specific and accurate and involves a simple pre-analytical sample manipulation; it is therefore suitable for routine analysis and provides data for samples within normal range as well as those with elevated levels. For the first time to our knowledge, cortisone levels are reported in dried blood spots from newborns. (C) 2011 Elsevier B.V. All rights reserved. |
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