De bepaling van thyroxine-bindend globuline in hielprikbloed van pasgeborenen ; bereiding van bloedvlekstandaarden 199003020

De bepaling van thyroxine-bindend globuline in hielprikbloed van pasgeborenen ; bereiding van bloedvlekstandaarden

[ [The determination of thyroxin binding globulin in dried bloodspots from neonates ; preparation of bloodspot calibrators.] ]

Elvers LH, Esmeijer A, Loeber JG

24 p in Dutch 1993

RIVM Rapport 199003020

Toon Nederlands

English Abstract
In the Netherlands neonatal screening on congenital hypothyroidism (CHT) is based on the determination of thyroxine (T4) in dried bloodspots on filterpaper. In 20 percent of the samples, those with the lowest T4 concentration, also thyrotropin (TSH) is measured. The positive predictive value (PV) of this screening strategy is low, about 6-8%. The reason for this is the low PV for T4. On January 1st 1993 the "TBG-project", subsidized by "Het Praeventiefonds", started in the CHT laboratories. The aim of this project is to examine whether the determination of thyroxine-binding globulin (TBG), in addition to T4 and TSH, can improve the positive PV. A commercial available radioimmunoassay kit for TBG in serum was modified to determine TBG in bloodspots on filterpaper. To correct for matrix effects there was a need for bloodspot standards. Two batches of bloodspot standards were prepared: TBG-IS and TBG-BO3. TBG-IS was prepared by mixing bloodcells with TBG-free serum, enriched with the International Standard for TBG (WHO 88/638). In TBG-BO3 the TBG-source was serum with a high TBG concentration. After calibration of TBG-BO3 in terms of TBG-IS the following concentrations were stated: 0, 45, 90, 180, 360, 720 and 1440 nmol/l. The range of TBG-BO3 in the RIA was good: 45 and 1440 nmol/l displaced 10% respectively 85% from the I-125-TBG. Conclusion: TBG-BO3 is suited to serve as blootspot standard in the TBG-project. There is a stock for 1 year for the 5 laboratories involved in this project.

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