FP11-5 Precursor-to-Product Ratios of Second-tier Samples in Newborn Screening Of Congenital Adrenal Hyperplasia

Program: Abstracts - Orals, Featured Poster Presentations, and Posters
Session: FP11-Pediatric Endocrinology
Clinical
Saturday, June 15, 2013: 11:00 AM-11:30 AM
Presentation Start Time: 11:20 AM
Room 104 (Moscone Center)

Poster Board SAT-601
Rebecca Ann Hicks*1, Jennifer Kuang Wei Yee1, Catherine S Mao1, Martin Kharrazi2, Steve Graham2, Fred Lorey2 and Wai-Nang Paul Lee1
1Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, CA, 2California Department of Public Health, Richmond, CA
Introduction: In newborn screening for congenital adrenal hyperplasia (CAH), samples with elevated 17-α-hydroxyprogesterone (17-OHP) above the birth weight-adjusted intermediate cutoff values are subject to steroid profiling (second-tier testing). Samples with elevated 17-OHP and a ratio of (17-OHP+androstenedione)/cortisol > 1 are considered to be presumptive positive for CAH. Under steady state conditions, the 17-OHP/11-deoxycortisol ratio in steroid synthesis is a reflection of the changes in 21-α-hydroxylase enzyme activity. The purpose of this study is to explore the use of direct precursor–to-product ratios as additional criteria for the evaluation of these second-tier samples.

Methods: Deidentified dried blood spot samples from confirmed CAH cases identified by newborn screen (N=8) and second-tier samples (N=197) were obtained from the California State Newborn Screening Program with the approval of the Institutional Review Board. Samples (~6.25 mm circular spots) were extracted and processed using methanol:water in the ratio of (9:1).  Deuterated steroids were added to each sample before extraction as isotope internal standards. 17-OHP, 11-deoxycortisol (11-DOC), androstenedione (A4) and cortisol in the blood spots were quantified using liquid chromatography-tandem mass spectrometry. The 17-OHP/11-DOC and 17-OHP/A4 ratios were calculated. 

Results: 17-OHP/11-DOC >1.6 (Pd) and 17-OHP/A4 >2 (Pa) in CAH-positive samples reflect diminished 21-α-hydroxylase activity and elevated androgen production. Using these ratios as criteria for decreased cortisol and increased adrenal androgen production, the second-tier samples were classified into four groups according to Pd, Pa, Nd (17-OHP/11-DOC <1.6) and Na (17-OHP/A4 <2). The proportions of adrenal profiles differed by birth weight (BW) greater or less than 1500 grams, with χ2(3, N = 197) = 83.38, p <0.001.

Conclusion: Steroid profiles of second-tier samples are clearly dependent on birth weight categories. Infants with BW <1500 had an androgen (A4)-producing phenotype associated with elevated 17-OHP, contributing to many false positives by the second-tier criteria. For infants with BW >1500, additional criteria based on 17-OHP/11-DOC and 17-OHP/A4 ratios may be helpful to further reduce the false positive rate in newborn screening of CAH.

Nothing to Disclose: RAH, JKWY, CSM, MK, SG, FL, WNPL

*Please take note of The Endocrine Society's News Embargo Policy at http://www.endo-society.org/endo2013/media.cfm

Sources of Research Support: Steroid analyses were performed at the Biomedical Mass Spectrometry facility at the Los Angeles Biomedical Research Institute at Harbor-UCLA, which is partly supported by the University of California Los Angeles Clinical and Translational Science Institute (UL1 TR000124) and the Metabolomics core of the Center of Excellence for Pancreatic Diseases (P01 AT003960).