▸ Very short (1.25 min) run to quantify relevant steroids to determine 21-CAH and 11-CAH. ▸ Material: dried blood spots. ▸ The method is very fast, robust, reliable and reproducible. ▸ False positive immunoassay results caused by EDTA can be avoided. ▸ Rapid method to confirm or discard the results received from the in newborn screening usually used ELISA assay on the same day.
Newborn screening for congenital adrenal hyperplasia (CAH) is usually done by quantifying 17α-hydroxyprogesterone using immunoassay. However, this test produces high rates of false positive results caused by cross reacting steroids. Therefore we have developed a selective and specific method with a short run time (1.25 min) for quantification of 17α-hydroxyprogesterone, 21-deoxycortisol, 11-deoxycortisol, 11-deoxycorticosterone and cortisol from dried blood spots. The extraction procedure is very simple and steroid separation is ensured on a BEH C18 column and an ultra-performance liquid chromatography–tandem mass spectrometry (UPLC–MS/MS). Analysis was done in positive ionization mode (ESI+) and recorded in multiple reaction monitoring mode (MRM). The method gave linear results for all steroids over a range of 5–200 (cortisol: 12.5–500) nmol/L with coefficients of regression >0.992. Absolute recovery was >64.1%. Across the analytical range the inter-assay coefficient of variation (CV) was <3%. Newborn blood samples of patients with confirmed 21-CAH and 11-CAH could clearly be distinguished from samples of unaffected newborns falsely positive on immunoassay. The method is not influenced by cross reactions as found on immunoassay. Analysis of dried blood spots shows that this method is sensitive and fast enough to allow rapid analysis and can therefore improve the newborn screening program.