Clinical usefulness of ELISA technique in the assessment of thyroid function

The clinical usefulness of Enzyme-linked Immunosorbent analysis (ELISA) for the assay of triiodothyronine (T3), thyroxine (T4) and T4 Uptake was studied in groups of clinically defined subjects. The following ranges of values were obtained in the normal control subjects: T3: 1.1-2.9 nmol/1; T4: 61.8-144 nmol/l; T4-Uptake: 0.7-1.34 and Free Thyroxine Index (FTI): 52.8-136. The diagnostic sensitivity of the technique was found to be reasonably good: showing good discrimination between hypothyroid, hyperthyroid and euthyroid subjects. Free thyroxine Index provided the best consistent correlation with the clinical states of the subjects particularly in subjects with altered binding protein levels. Several advantages offered by ELISA technique over radiochemical methods such as freedom from radiation hazards, non-requirement of specialized laboratories with expensive equipment and cheaper reagents with relatively longer shelf lives, make this procedure particularly suitable for use in small laboratories.