An evaluation of absorbent granule kits for determining serum thyroxine concentration and free thyroxine index in the diagnosis of thyroid function.

SYNOPSIS Serum thyroxine concentrations were measured in five groups of subjects using Thyopac-4 kits containing absorbent granules. A free thyroxine index was determined from these estimations in association with triiodothyronine uptake ratios using Thyopac-3 kits. The values obtained were compared with thyroxine concentrations and T-7 values using kits containing resin sponges. Measurements with the absorbent granule kits and in particular the calculated free thyroxine index have proved very valuable in distinguishing between euthyroid, hyperthyroid, and hypothyroid subjects. The advantages of these kits over resin sponge kits are discussed.