RT Journal Article SR Electronic T1 A New Economical Method for Determination of Triiodothyronine (T3) Uptake Using Talc Tablets JF Journal of Nuclear Medicine Technology JO J. Nucl. Med. Technol. FD Society of Nuclear Medicine SP 207 OP 210 VO 6 IS 4 A1 Wayne Lin, Wen-Chiao A1 dos Remedios, Leo V. YR 1978 UL http://tech.snmjournals.org/content/6/4/207.abstract AB The determination of T3 uptake is necessary to find the free thyroxine index, increasingly used as the simplest accurate measure of thyroid dysfunction. A T3 uptake determination requires a reproducible, readily automated, and cost-effective method of adsorbent separation. Five adsorbent separating reagents were studied: hemoglobin-coated charcoal, dextrancoated charcoal, magnesium carbonate, anion-exchange resin, and talc tablets. Of these, binding efficiency was best with talc tablets. Talc binding was insensitive to incubation time, eliminating problems associated with other reagents. To maintain the conventional normal range for T3 uptake (25-35%), the quantities of talc, tracer, and serum used required adjustment. Results obtained with talc were compared to those obtained with a commercial kit, using paired sera from 897 patients. The correlation coefficient was 0.95 (P<0.0005). The coefficients of variation (CV) for 36 runs were 4.6%, 2.3%, and 2.1% inter-assay, and 3.3 %, 1.7%, and 1.04% intra-assay for hypothyroid, euthyroid, and hyperthyroid controls, respectively.