Steroid profile in dried blood spots by liquid chromatography tandem mass spectrometry: Application to newborn screening for congenital adrenal hyperplasia in China

Background: Newborn screening for congenital adrenal hyperplasia (CAH) using 17-hydroxyprogesterone dissociation-enhanced, lanthanide fluorescence immunoassay (DELFIA) generates a large number of false positive results. The present study aimed to improve the sensitivity of the CAH neonatal screening by including second-tier steroid profiling in dried blood spots (DBS) using liquid chromatography tandem mass spectrometry (LC-MS/MS). Methods: We developed and validated a LC-MS/MS method for simultaneous determination of six steroids in DBS, including androstenedione, testosterone, 17-hydroxyprogesterone, 11-deoxycortisol, 21-deoxycortisol, and cortisol. Two 5-mm blood spots were eluted by internal standard working solution. We analyzed 1170 DBS samples from neonates to determine gestational age-specific reference intervals. In order to test the specificity of the second-tier method, we analyzed 707 cards with a positive screening by DELFIA. Results: Values of intra-and inter-day precision coefficients of variance and accuracy were 2.0%-13.3% and 85.8%-114.5%, respectively. Recovery ranged from 85.0% to 106.9%. The lower limit of quantification was 0.5 ng/mL for 21-deoxycortisol, 0.25 ng/mL for 17-hydroxyprogesterone and cortisol, and 0.1 ng/mL for testosterone, androstenedione, and 11-deoxycortisol. In addition, the linearity range was 0.25-50 ng/mL (R2 > 0.99). According to the 17-hydroxyprogesterone levels and ratios of (androstenedione + 17-hydroxyprogesterone)/ cortisol in the 707 positive screening samples, 77 neonates should receive recall visit. The number of false positive results reduced by 89.1%. Totally, 18 newborns were diagnosed with 21-hydroxylase deficiency, one with P450 oxidoreductase deficiency and one with 118-hydroxylase deficiency. With two-tier screening, the positive predictive value increased to 26.0%. Conclusions: The second-tier steroid profiling by LC-MS/MS reduced the false-positive rate and improved the positive predictive value of CAH screening. We suggest applying this steroid profiling assay as a second-tier test for CAH screening in China.