The results of an 125I-labeled IRMA for TSH counted by liquid scintillation counting on TopCount and on a gamma counter are shown in Figure 3. The standard curves are essentially the same for the two methods of quantitation. Direct counting of immunoassay microplates with TopCount eliminates the need to transfer individual microplate wells to tubes for counting in a gamma counter. The counting efficiency for 125I in TopCount, using MicroScint-O, is higher than 50%.
The Packard TopCount Microplate Scintillation and Luminescence Counter, PicoPlates, and the specially formulated scintillation cocktail, MicroScint- O, provide results from samples in organic solvents or on solid supports equivalent to those obtained with a conventional liquid scintillation counter or gamma counter. Up to 50% sample loads of organic solvents may be used. With small sample loads, counting efficiencies are comparable to conventional LSC. For assays prepared in the microplate, TopCount provides quantitation in the same format. This results in increased throughput, less sample handling, and significant savings in reagent and waste disposal costs.
The enzyme inhibition samples were supplied by Dr. Russell Lingham; Merck, Sharpe, and Dohme; Rahway, New Jersey, U.S.A. The TSH immunoassay work was performed by Dr. Alain Baret; Labratoire D'Analysis Medicales; Nantes, France.