1982 Volume 11 Issue 3 Pages 222-230
A new radioimmunoassay method (Amerlex® Free T4) for measurement of the serum concentration of free thyroxine (FT4) was evaluated with the following results.
1. The estimated values were almost constant during incubation for 30 to 240 min at37°C.
2. The coefficients of variation, which were 2.5-3.5% (within assay) and 5.2-16.5% (between assays), were acceptable for clinical tests.
3. The FT4 values of sera with added T4 determined by this method were identical to those estimated by computational analysis.
4. The FT4 concentration determined by this method in normal sera was 1.42±0.24ng/dl (normal range: 0.90-1.90ng/dl). The serum FT4 concentration was increased in hyperthyroidism, decreased in hypothyroidism, at the lower limit of normal in pregnancy (18-26 weeks) and liver cirrhosis, and within normal limits in familial TBG excess and TBG deftciency.
5. The FT4 values determined by this method correlated well with those determined by computational analysis, and equilibrium dialysis and with the FT4 index.
