Olthof Anouk, Bouva Marelle J, Claahsen-van der Grinten Hedi L, Westra Dineke, Dekkers Eugènie, Heijboer Annemieke C, Hannema Sabine E, Boelen Anita
Endocrine Laboratory, Department of Laboratory Medicine, Amsterdam Gastroenterology Endocrinology Metabolism, Amsterdam UMC location University of Amsterdam, Amsterdam, The Netherlands.
Endocrine Laboratory, Department of Laboratory Medicine, Amsterdam Gastroenterology Endocrinology Metabolism, Amsterdam UMC location Vrije Universiteit Amsterdam, Amsterdam, The Netherlands.
Arch Dis Child. 2025 Aug 19. doi: 10.1136/archdischild-2025-328929.
Congenital adrenal hyperplasia (CAH) due to 21-hydroxylase deficiency is an inherited adrenal steroid synthesis disorder included in Dutch newborn screening (NBS) since 2002. Screening involves measuring 17-hydroxyprogesterone (17-OHP) in dried blood spots (DBS) with gestational age-adjusted cut-offs. Since October 2021, a second-tier 21-deoxycortisol (21-DF) test has replaced the 17-OHP measurement in a second heel prick after inconclusive results. This study evaluates the performance of the second-tier test from 1 October 2021 to 30 September 2023.
17-OHP was measured by immunoassay in regional NBS laboratories. DBS with inconclusive and positive 17-OHP results was sent to Amsterdam UMC for 21-DF measurement by liquid chromatography tandem mass spectrometry. Genetic analysis of , , and was performed on DBS from newborns with false-positive second-tier results.
Over 2 years, 21-DF was measured in DBS of 147 newborns (=0.04%). Twenty newborns were directly referred to a paediatric endocrinologist based on positive 17-OHP results: 15 had a positive 21-DF and were diagnosed with classical CAH (genetically confirmed), while five were first-tier false-positives. Of 127 newborns with inconclusive 17-OHP results, three had a positive 21-DF and were referred but not diagnosed with CAH: second-tier false-positives. In total, 8/23 referred newborns were false-positives. Genetic analysis of six false-positive second-tier DBS showed pathogenic variants in five.
The modified protocol improved CAH screening by preventing 127 heel pricks in 2 years and reducing unnecessary referrals (currently 2.4%, previously 7.7%). 5/6 false-positive second-tier tests were most likely due to non-classical CAH. Further optimisation of cut-offs may prevent these false-positives.
