ESPE Abstracts

In Belgium, neonatal TSH screening for congenital hypothyroidism has been performed between day 3 and 5 of life since the late seventies. In January 2015, a policy of early discharge of healthy neonates was implemented so that the neonatal screening strategy had to be adapted. Between January 2015 and September 2019, dried blood spot sampling was mostly collected at home AFTER discharge at 72 h of life (Newborn Screening Strategy 1 (NBS1)). After October 2019, sampling was mostly collected in hospital BEFORE discharge at 48 h of life (Newborn Screening Strategy 2 (NBS2)). Our primary aim was to compare neonatal TSH screening results with sampling at 48 h and at 72 h of life. Our secondary aim was to compare home and hospital sampling in terms of screening efficiency. This retrospective study includes live births ≥ 37 weeks of gestation, screened by the U.L.B. Newborn Screening Center between January 2019 and December 2021. We compared the characteristics of newborns screened < 72h to those screened ≥72 h. We also compared TSH screening results obtained with NBS1 and NBS2. The whole blood TSH cut-off value to request a second DBS sample is determined using the p99.5 calculated on the newborn population. A total of 54,700 newborns were included. The median TSH at various time points is shown in the Table.

The false positive rate of NBS was similar: 0.12% in newborns screened <72h and 0.13% in newborns screened. 72h. As expected, the age at receipt of NBS result was younger with NBS2 (7.0 vs 5.8 days, P<0.05). NBS2 resulted in a slightly higher screening coverage (calculated on 14911 Births) (99.9% vs 99.7%, P 0,2328). Full term newborn TSH screening performed before discharge as soon as 48 h of life is a valid strategy as it does not increase the false positive and recall rates and allows for a better screening coverage. The same TSH cut-off can be used for screening at 48 and 72 h of life. Sampling at home entails increased costs that need to be factored in.