Abstract
Glucose meter performance specifications provide limits for 95% of results, which is the same as total error. A popular total error model is that total error equals (average) bias plus 2 times imprecision. This model has been used to specify combinations of average bias and imprecision that satisfy total error goals. But this model is incomplete and its conclusions are suspect. It is shown that when interferences occur in glucose meters as exemplified by hematocrit interference, the total error model proposed by Boyd and Bruns cannot distinguish between meters that differ in performance. The CLSI standard EP21-A, does not have this problem because it directly estimates total error bypassing the need for a model. An example illustrates these points.