Confirmation of neonatal screening: reference intervals and evaluation of methodological changes in TSH measurement

Neonatal reference values for serum thyrotropin are scarce and comprise only small numbers of patients. During 2006, changes were made in IMMULITE kits for TSH measurement. To validate methodological changes, 80 serum samples from patients were evaluated and to establish reference intervals, 334 neonates and infants were analyzed (divided into 4 groups). Group 1 (G1) (48-72 h of life) (n=153), group 2A (G2A) (7-10 days of life) (n =65), group 2B (G2B) (11- 14 days of life) (n= 35), group 3 (G3) (28-40 days of life) (n =81). Current kits overestimate TSH results by 26 to 37%; TSH (mIU/L) reference intervals (percentile 2.5 ― 97.5) were G1 (1.1-12.7), G2A (1.8-9.8), G2B (1.1-7.1) (p