Correlation between free thyroxine level and free thyroxine index in the diagnosis of thyroid function

As part of an effort to establish national radioimmunoassay reagent production, the National Atomic Energy Agency has ''assembled'' radioimmunoassay kits for thyroid function testing which include total thyroxine (T4), triiodothyronine (T3) uptake and free T4 assay. The paper reports the results of a clinical study conducted to assess the clinical validity of the kits. A total of 157 subjects collected serum samples which were assayed for levels of free thyroxine (fT4), total T4 (tT4) and T3 uptake. These samples were also assayed for levels of fT3, tT3 and sensitive thyroid stimulating hormone (S-TSH). The subjects consisted of 43 healthy euthyroid subjects (40 females and 3 males, with an age ranging from 23 to 45 years) and 114 patients (103 of whom were females) with an age ranging from 2 to 63 years and having various thyroid disorders and severe non-thyroidal illnesses. The results of free T4 assay and the free thyroxine index (fT4I) calculation were correlated and the clinical status of the thyroid as well as other biochemical parameters compared. 3 figs, 2 tabs