The use of IRE-Medgenix serum TSH IRMA in neonatal screening for congenital hypothyroidism.

The TSH-IRMA kit, manufactured by IRE- Medgenix is an immunoradiometric assay for the measurement of thyroid stimulating hormone (TSH) in human serum. This kit was modified and tested for its possible use as routine method in neonatal screening for congenital hypothyroidism (CHT). In the present screeningprocedure TSH is measured in a small (1/4-1/8)-inch bloodspot. For this reason bloodspot calibrators of the 2nd IS for TSH 80/558 were prepared on filterpaper. The minimal detectable dose was 0,010 muU TSH in a (1/4-1/8)-inch bloodspot. There was a good correlation between TSH measured in serum and in bloodspots: "spot" = 1,02 * "serum" + 0,04 (r=0,0988, N=51). The intra- and interassay coefficient of variation was 3.2%, 3.5%, 6.3% and 6.9%, 6.1% 10.2% respectively for bloodspot samples containing 12.2, 19.1 and 29.6 mU/ll serum. In comparison with the current RIA-method used for screening on TSH, this modified IRMA gave better results with respect to analytical performance. The IRMA is also less time consuming than the RIA and can be automated easier. Conclusions: the analytical performance of the IRE- Medgenix TSH-IRMA is very good. The kit, modified for the measurement in bloodspots, can be used in a neonatal CHT screening programme.RIV