[TSH levels in newborn with low and very low birth weight vs rescreening for congenital hypothyroidism].

Unlabelled: A disorder of thyroid function, as stated by various references, is very common among children with low and very low body weight. Also, the concentration of thyroid hormones in this group differs from that of neonates full term with the adequate body weight. In 1998, in southeastern Poland, a repeated screening for TSH level in blood spots on filter paper was introduced among neonates with low and very low birth-weight. The purpose of this work was the exclusion of late appearing transient hypothyroidism, as well as the verification of falsely positive results in the basic test. Newborns with low and very low birth-weight comprise nearly 5% of live births in the region. During 1998-2001, 4,445 children with body weight below 2500 g were tested. Tests for TSH level in blood on filter paper were carried out in neonates between three and six days of age and also at the end of the first month of life. TSH levels in blood on filter paper were estimated using the LIA method (Byk Sangtec Diagnostica). The results were divided into two groups: those with correct TSH, that is < 15 mIU/L, and those with a raised level 3 15 mIU/L. The repeated test confirmed the correct result in nearly 100% of the neonates, while in 20 (0.5%) showed the increase of TSH level above 15 mIU/L. TSH and fT4 monitoring followed by serum determinations during treatment showed primary hypothyroidism in 10 children and hyperthyrotropinemia in 5 cases.

Conclusion: 1) It would appear advisable to introduce a repeated routine screening for hypothyroidism in the group of low and very low birth-weight neonates, as this permits the identification of cases with raised values requiring verification. 2) In addition, thanks to the repeated screening we avoid false negative pitfalls in low and very low birth-weight neonates, i.e. primary congenital and transient hypothyroidism.