Determination of specimen storage conditions for measuring isoagglutinin titers.

Background: This study aimed to determine the optimal specimen storage conditions for isoagglutinin titration by changing storage time and temperature.

Study Design And Methods: Serum specimens from 60 individuals were stored at room temperature (RT, 25 °C) or at 4 °C and tested every 24 hours until 96 hours by the immediate spin (IS) method and the anti-human globulin method using dithiothreitol (DTT-AHG). These titer results were compared with the titers which were measured when the samples arrived. The titer endpoint was defined as the highest dilution, with clinically meaningful differences defined as more than 4-fold differences (two serial dilutions) in titer.

Results: Of the specimens stored at RT for 24, 48, 72, and 96 hours, 5%, 12%, 12%, and 12%, respectively, showed two-fold (one dilution) differences by the IS method, and 8%, 8%, 8%, and 10%, respectively, showed two-fold (one dilution) differences with the DTT-AHG method. Of the specimens refrigerated for 24, 48, 72, and 96 hours, 8%, 10%, 13%, and 13%, respectively, showed two-fold (one dilution differences) by the IS method, and 13%, 12%, 12%, and 12%, respectively, showed two-fold (one dilution) differences with the DTT-AHG method.

Conclusions: Specimens stored for up to 96 hours at RT and 4 °C showed similar titers using the IS and DTT-AHG methods. These findings suggest that tests can be scheduled regularly.