ESPE Abstracts

Objectives: Congenital adrenal hyperplasia (CAH) due to 21-hydroxylase deficiency (21-OHD) is included in the Dutch Newborn Screening (NBS) since 2002. NBS for CAH consists of a 17-hydroxyprogesterone (17-OHP) measurement in dried blood spots (DBS) with gestational age-adjusted cutoffs. Previously, a second heel prick was performed in newborns with inconclusive results to reduce false-positives. In October 2021, 21-deoxycortisol (21-DOCL) was introduced as a second tier test to replace the second heel prick. The present study aims to evaluate the performance of the second tier between 1 October 2021 and 30 September 2023.

Methods: At the Amsterdam UMC Endocrine Laboratory, 21-DOCL and 17-OHP concentrations were determined by LC-MS/MS in DBS of newborns with an inconclusive 17-OHP screening result. DBS of newborns with a positive 17-OHP were also measured in the context of this evaluation. A positive initial 17-OHP or an inconclusive 17-OHP/positive 21-DOCL is seen as a positive screening. Diagnoses were confirmed after referral of a positive screening to a pediatric endocrinologist by genetic analysis of CYP21A2, the gene encoding 21-hydroxylase.

Results: Over a period of two years, 21-DOCL was measured in DBS of 147 newborns (0.04%). Twenty of them were directly referred to the pediatric endocrinologist based on a positive 17-OHP. Fifteen of these twenty also had a positive 21-DOCL and were diagnosed with 21-OHD, while the other five had a negative 21-DOCL and no confirmed 21-OHD. 127 newborns had an inconclusive 17-OHP, of which three had a positive 21-DOCL and were referred, but did not have 21-OHD. In total, twenty-three newborns were referred, of whom fifteen were diagnosed with 21-OHD, resulting in eight false-positive referrals; five based on the positive 17-OHP and three on an inconclusive 17-OHP and a positive 21-DOCL. The other 124 newborns did not have 21-OHD. One false-negative result was reported based on 17-OHP screening result below cut-off value. This child already received treatment before the heel prick was performed, due to family history.

Conclusion: The modified protocol has improved the CAH screening by preventing 127 second heel pricks in two years and reducing the number of unnecessary referrals. However, three false-positive 21-DOCL results were identified. Genetic analysis of CYP11B1, HSD3B2 and POR is being performed and will hopefully elucidate the reason for the false-positive 21-DOCL, as this is seen as a highly specific marker for 21-OHD. If not, cut-off values for 21-DOCL need to be optimized in order to prevent unnecessary false-positive results in the future.