Nation-wide TSH-screening with low recall rate

Abstract

The laboratory results from the Danish neonatal TSH screening programme for congenital hypothyroidism are reported for a period of 2 years. The screening was based on a single determination of TSH in blood samples taken on the fifth day of life (PKU-filterpaper). The TSH assay (double antibody radioimmunoassay) has a sensitivity of 10 mU TSH/1 blood and a precision of 20–30%. 127,111 samples have been tested. In 3% TSH was >10μ/l and in 0.64% >25 mU/1. The cut-off point was fixed at 25 mU TSH/1. Values above this level were corroborated by a T-4 radioimmunoassay on the original blood specimen. TSH >25 mU/1 together with T-4<45 nmol/1 blood was found in 37 samples. In 18 samples with TSH >25 mU/1 there was no material left for the T-4 determination. These 55 samples (37 + 18) resulted in a request for a venous sample (recall rate 0.043 %). An elevated TSH was verified in 32 of the 55 samples. The repeat samples were collected on average on the 25th day after birth. Three of the 32 babies were clinically diagnosed before the screening result was available.

Key-words:

• congenital
• hypothyroidism
• screening
• thyrotropin
• thyroxine
• radioimmunoassay