Adapting serum TSH IRMA kit for estimating TSH in whole blood - for use in neonatal screening of congenital hypothyroidism

In order to screen neonates for congenital hypothyroidism, collecting large amount of blood (1-2 mL from neonates) is difficult and unnecessary if, TSH can be estimated reliably in small amount (i.e. ≈ 500μL) of whole blood. As whole blood TSH kits are not available we have tested five commercial serum TSH IRMA kits for their suitability to measure TSH in whole blood samples. Serum TSH standards were adjusted to 50% hematocrit by adding equal volume of washed, packed RBCs from normal healthy volunteers. This reconstituted whole blood standards were used to evaluate the performance by analyzing 47 whole blood samples in each of the five kit studied. Results: It was possible to measure TSH in whole blood in all the kits studied without any RBC interference. Significant correlation was obtained between the serum TSH values and the whole blood TSH values. IZOTOP hTSH-IRMA Kit y = 1.0823x + 0.2516, r = 0.992, n = 47, IMMUNOTECH hTSH-IRMA Kit y = 1.0067x + 0.7377, r = 0.982, n = 47, Coat -A-Count hTSH-IRMA Kit y = 0.9874x + 0.387, r = 0.986 n = 47, RADIM hTSH-Kit y = 0.9842x + 0.7518, r = 0.991, n = 47. While this study demonstrates the possibility of measuring TSH in whole blood using the adult samples, the real scenario of using such a methodology in neonates need to be demonstrated using the neonate samples. (author)