Effect of various sample-handling conditions on radioassay results.

Samples brought to the laboratory for routine radioassay often have been under suboptimal conditions. We compared the effect of some sample-handling conditions on the values for T3, T3 resin uptake (T3RU), T4, thyrotropin, cortisol, and prolactin in serum as determined by radioassays. Blood was collected in three separateplain red-top Vacutainer Tubes from each of six subjects. Serum was separated from one of the three tubes, divided into portions, and frozen within 1 h of collection. Another tube from each patient was allowed to sit at room temperature for 7 h and then the serum was separated, apportioned, and frozen. The third tube from each patient was allowed to sit at room temperature for 7 h, then left overnight in the refrigerator and the serum separated and frozen after a further 17 h. All assays were done with commercially available kits: T4, T3RIA, and thyrotropin kits from Beckman Instruments Inc., Fullerton, CA 92634; T3RU kits from E.R. Squibb and Sons Inc., Princeton, NJ 08540; cortisol kits from Clinical Assays, Cambridge, MA 02139; and prolactin kits from Abbott Laboratories, Diagnostics Division, North Chicago, IL 60064. We could detect no significant detrimental effect of these various samplehandling conditions on the results of routine radioassays.