Newborn screening for congenital adrenal hyperplasia (CAH) is limited because of high rates of false-positive values. However, adjusting threshold levels of 17α-hydroxyprogesterone (17-OHP) to reflect gestational age and birth weight might be a safe and efficient strategy to improve screening for CAH, according to study results published in The Journal of Clinical Endocrinology & Metabolism.

The high false-positive rate of newborn screening for CAH, yielding up to 1% false-positive results, has been one of the most significant limitations to newborn screening programs. For this reason, several approaches have been tested to improve diagnosis of CAH.

The National Newborn Screening Program in Israel has been using a unique combination of cutoffs based on multiple tiers of 17-OHP cutoff values stratified according to gestational age and birth weight to reduce false-positive rates of newborn screening for classical CAH. In this study, the researchers reported results 10 years after implementing this strategy.

The newborn screening program included more than 1.3 million newborns born between 2008 and 2017, including 88 newborns diagnosed with CAH. Most of the cases (84 neonates) were detected using the screening program. The incidence rate in the Jewish population was 1:20,500 live births (53 cases), and in the Arab population, the incidence rate was 1:9500 live births (34 cases).

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The results indicated that using cutoffs values of 17-OHP adjusted to both birth weight and gestational age was associated with high positive predictive value (16.5%), despite low false-positive rate (0.03%). The sensitivity and specificity of the newborn screening program were 95.4% and 99.9%, respectively.

Only 4 newborns with CAH were missed by the screening protocol (false negatives). These patients were diagnosed with simple virilizing type and not classical salt-wasting CAH.

“Based on our ten years of experience, we recommend the implementation of this novel, two parameter-adjusted approach for [newborn screening] of classical CAH, in [newborn screening] programs worldwide,” concluded the researchers.

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Reference

Pode-Shakked N, Blau A, Pode-Shakked B, et al. Combined gestational age- and birth weight-adjusted cutoffs for newborn screening of congenital adrenal hyperplasia [published online March 13, 2019]. J Clin Endocrinol Metab. doi:10.1210/jc.2018-02468