Efficacy of congenital hypothyroidism neonatal screening in preterms less than 32 weeks of gestational age: more evidence.

Objective: To evaluate the double screening performed for congenital hypothyroidism (CH) to preterm infants < 32 weeks of gestational age (GA) between 1994 and 2003. Infants and Methods: TSH was assessed by IFMA. Infants were classified as: term (T) (> 37 weeks GA); preterm (PT) (33-37 weeks GA); and very preterm (VPT) (<= 32 weeks GA). Results: In 585,221 screened infants, CH was confirmed in 228 T, 23 PT and seven VPT. An increasing incidence of CH was found with decreasing GA, affecting 1:1,603 PT and 1:585 VPT. PT infants had 1.5 times more risk than fullterm infants of suffering CH, and VPT 4 times more. Only 4/7 affected VPT had an adequate double screening as requested. Three had elevated TSH values in the first sample and in one a normal TSH (10.3 mIU/l) at 3 days rose to 240 mIU/l after day 15. In the remaining three VPT, TSH in the unique filter paper sample (21 to 34 days) was markedly elevated. Conclusions: Our findings reinforce the need for awareness in neonatal settings for adequate screening of VPT infants. Screening in the first week of life was effective in detection of most but not all affected VPT. Larger studies are needed in order to establish accurate screening recommendations for VPT newborns. Until this step is reached, repeated screening is advised in these infants.