TY - JOUR
T1 - Measuring free thyroxine levels in neonatal heel-prick samples
AU - Boelen, Anita
AU - van Veen, Marja
AU - Verkerk, Paul H.
AU - Diependaal, Guido
AU - Loeber, Gerard
AU - Elvers, Bert
AU - Endert, Erik
PY - 2013
Y1 - 2013
N2 - The Dutch neonatal screening scheme for Congenital Hypothyroidism (CH) is primarily based on the determination of thyroxine (T4) in filter paper blood spots. In the lowest 5% of T4 values, thyroxine binding globulin (TBG) is measured in order to be able to correct for occasional low TBG levels. However, because the commercial TBG kit has been withdrawn from the market, alternative strategies are needed to be explored including the assessment of free T4. We evaluated the Neonatal Free Thyroxine (fT4) enzyme immunoassay (EIA) kit of Bio-Rad. FT4 as measured in a daily run of random samples correlated with T4. We also observed a correlation between fT4 and T4, and between fT4 and T4/TBG ratio in blood spots with low T4 concentrations. The correlation between fT4 and T4 in blood spots of proven CH-patients was highly significant. ROC curves were constructed for the fT4 assay and the T4/TBG ratio based on 27 CH patients and 215 controls with a complete set of data. The curves of both assays seemed to be rather similar. We conclude that the validity of the fT4 and the T4/TBG-approach seems to be the same. A study with a larger sample size giving the same or even more favorable results for the fT4-approach is necessary before we will change the present CH protocol
AB - The Dutch neonatal screening scheme for Congenital Hypothyroidism (CH) is primarily based on the determination of thyroxine (T4) in filter paper blood spots. In the lowest 5% of T4 values, thyroxine binding globulin (TBG) is measured in order to be able to correct for occasional low TBG levels. However, because the commercial TBG kit has been withdrawn from the market, alternative strategies are needed to be explored including the assessment of free T4. We evaluated the Neonatal Free Thyroxine (fT4) enzyme immunoassay (EIA) kit of Bio-Rad. FT4 as measured in a daily run of random samples correlated with T4. We also observed a correlation between fT4 and T4, and between fT4 and T4/TBG ratio in blood spots with low T4 concentrations. The correlation between fT4 and T4 in blood spots of proven CH-patients was highly significant. ROC curves were constructed for the fT4 assay and the T4/TBG ratio based on 27 CH patients and 215 controls with a complete set of data. The curves of both assays seemed to be rather similar. We conclude that the validity of the fT4 and the T4/TBG-approach seems to be the same. A study with a larger sample size giving the same or even more favorable results for the fT4-approach is necessary before we will change the present CH protocol
U2 - https://doi.org/10.1016/j.cca2013.04.004
DO - https://doi.org/10.1016/j.cca2013.04.004
M3 - Article
C2 - 23588061
SN - 0009-8981
VL - 423
SP - 51
EP - 55
JO - Clinica chimica acta; international journal of clinical chemistry
JF - Clinica chimica acta; international journal of clinical chemistry
ER -