An Investigation into the Effect of Reagent Volume on the Spin Indirect Antiglobulin Test

. Three polyspecific antiglobulin reagents were tested in a spin antiglobulin technique with 51 antibodies of varying blood group specificities in which the volume of antiglobulin reagent used ranged from 1 volume (35 μl) to 3 volumes (105 μl). Statistical analysis of results showed that a significant decrease in avidity and agglutination scores occurred as the volume of antiglobulin reagent used was increased (‘volume effect’). The volume effect was shown by 33/51 (65%) of antibodies with all three antiglobulin reagents and by 48/51 (94%) of antibodies with at least one antiglobulin reagent. Only 3/51 (6%) failed to show the volume effect with all three antiglobulin reagents.