Reevaluation of the Neonatal Screening Test for Congenital Hypothyroidism

Kang, So Young; Chang, Young Pyo; Yu, Jeesuk

Abstract

PURPOSE
We performed this study to compare the TSH and free T4 levels according to gestational age and birth weight, and to reevaluate the cut-off values in the neonatal screening test for congenital hypothyroidism.
METHODS
Total 2,133 neonates(1,749 healthy newborns and 384 sick neonates) were screened in Dankook University Hospital from May 2000 to January 2003. Neonates with abnormal TSH values (higher than 20 microliterU/mL) or abnormal free T4 levels(lower than 1 ng/dL) were recalled to recheck the thyroid function test. At that time, physical examinations and history-taking regarding perinatal problem, medication history, and mother's illness were undertaken.
RESULTS
Serum TSH and free T4 values revealed no significant difference according to sex, delivery type, and Apgar score. The free T4 levels showed statistically significant differences, with gestational age or birth weight(P<0.01). The recall rate of neonates due to abnormal screening test was 7.48 percent. Compared with original cut-off values, the recall rate of the new cut-off values setted to TSH higher than 20 microliterU/mL or free T4 lower than 0.64 ng/dL decreased from 7.48 percent to 4.8 percent in the healthy group. But, it compromised sensitivity when applied to the sick group.
CONCLUSION
In this study, neonatal free T4 levels were significantly different according to birth weight, gestational age, and the presence of compromised condition. Although the recall rate by TSH >20 microliterU/mL or free T4<1 ng/dL was relatively high, it was impossible to set up new cut-off values without compromising sensitivity. We think studies including a larger study population will be required to change the cut-off values.