Supplementary Material for: Neonatal Screening for Congenital Adrenal Hyperplasia in Denmark: 10 Years of Experience

Introduction: Early detection of salt-wasting congenital adrenal hyperplasia (SW-CAH) is important to reduce CAH related morbidity. However, neonatal screening has shown to have a low positive predictive value (PPV), especially among preterm newborns. Here, the Danish CAH screening is evaluated by comparing incidence and morbidity of SW-CAH ten years before and after introduction of screening. Furthermore, sensitivity, specificity and PPV are determined. Methods: All newborns in Denmark born during 1999-2018 and diagnosed with SW-CAH were identified in the Danish National Patient Registry and/or at the Department of Clinical Genetics, Rigshospitalet. Newborns with a positive neonatal CAH screening were identified at Statens Serum Institut. Correct diagnosis was evaluated by medical record review. Results: A total of 65 newborns with SW-CAH were identified. The incidence of SW-CAH was 5:100,000 both before and after introduction of screening. Performance of sensitivity and specificity of the screening were 97% and 100%, respectively, and the PPV was 55% for the given period. Stratified according to gestational age, the PPV was 33% and 61% for pre -and fullterm newborns, respectively. Though not significant the proportion of newborns presenting with salt-wasting crisis decreased after introduction of screening from 29% vs. 10% (p=0.07). Discussion and Conclusion: Neonatal screening for SW-CAH has not led to an increase in the incidence of newborns diagnosed with SW-CAH. The screening algorithm has effectively identified newborns with SW-CAH. After 2009, there was a tendency towards a lower proportion of newborns with salt-wasting crisis at diagnosis. Finally, the study emphasizes the benefits of using second-tier screening as well as repeated screening of premature newborns.