Serum thyroxine determination by saturation analysis: a new method and statistical approach.

Abstract

ABSTRACT A new method for the measurement of total serum thyroxine (T4) by saturation analysis is presented along with technical details. Its main advantage over previously published methods is its sensitivity of 0.3 picomoles T4 (corresponding to 0.23 ng T4 or 152 pg iodine). It thus allows the measurement of serum thyroxine in very small volumes of human serum (7 μl) and, for the first time, in mouse serum. The use of Sephadex to extract thyroxine from the plasma gives more reproducible results and avoids the need to evaporate the extract to dryness, as in current methods. A high speed digital computer was used for handling data processing. A new statistical algorithm was built into a code called REGSAT which is extensively described. This procedure allowed unskewed predictions of thyroxine levels in the samples and an estimate of the standard curves resolving power.