Evaluation of a commercial kit for microchromatographic quantitation of hemoglobin A2 in the presence of hemoglobin S.

Commercial microcolumns introduced in 1976 by Helena Laboratories ("Hb A2 Quik Column") and by Isolab, Inc. ("Quik-Sep") provide a rapid, simple, accurate method for quantitation of hemoglobin A2 (Hb A2). However, these kits cannot be used for the quantitation of Hb A2 in the presence of slow-moving variants such as Hb S. Recently, Isolab, Inc., produced a new kit ("Quik-Sep Improved Hb A2 Test") for quantitation of both Hb A2 and Hb S. We compared results obtained with the new Isolab kit to results obtained with the original Tris/HCl method for quantitation of Hb A2 and Hb S. Blood was drawn from persons with sickle cell trait (A/S), sickle cell anemia (S/S), sickle cell/beta+ thalassemia (S/beta+ thal) and sickle cell/beta 0 thalassemia (S/beta 0 thal) and percentages of Hb A2 and Hb S were determined by each method. We found no significant differences in Hb A2 percentages by the two methods, and the coefficients of variation were similar. Both methods showed only slight overlap of Hb A2 values from subjects with some form of beta thalassemia and those with A/S or S/S. However, the Tris/HCl method consistently gave values for Hb S that were higher and closer to those expected, suggesting that the Isolab kit does not accurately quantitate Hb S.