Neonatal screening tests are used for the screening of genetic, endocrine and metabolic diseases. Preterm newborns have a higher false-positive and false-negative results in neonatal screening. The objective of this study was to estimate the prevalence of false-positive and false-negative results in the neonatal screening tests for phenylketonuria, congenital hypothyroidism, biotinidase deficiency and congenital adrenal hyperplasia (CAH) in preterm newborns in Curitiba, to analyze other factors that influences the results and to evaluate the adherence to the newborn screening guideline for preterm newborn. A cross-sectional study with prospective data collection was carried out in 11 hospitals from March to December 2015. The results were compared with the results of the screening tests performed on the term newborns. A total of 1753 preterm newborns and 18 028 term newborns were included. Only 486 (28%) of the preterm newborn performed the second dried blood spot, according to guideline. The prevalence of false-positive in preterm newborn for phenylketonuria was 1:150, for congenital hypothyroidism was 1:133, for biotinidase deficiency was 1:447 and for CAH was 1:5,6. Early dried blood spots, collected before 48 hours postnatal age, showed a higher risk of false-positive results for congenital hypothyroidism and CAH (26.78 and 16.41, respectively). Early sample collection did not influence the results of the screening tests for phenylketonuria and biotinidase deficiency. Only one patient had delayed thyroid stimulating hormone (TSH) elevation. There were no reports of false-negative results.
Conclusions: Prematurity and early collection were considered as risk factors for higher frequency of false-positive in neonatal screening tests of CAH and congenital hypothyroidism. A second dried blood spot for screening test is recommended to diagnose cases of delayed TSH elevation. Efforts should be made to improve the proper collection of tests in preterm infants to avoid false-negative results.
27 - 29 Sep 2018
European Society for Paediatric Endocrinology