A proposal for further standardization of red blood cell glucose 6-phosphate dehydrogenase determinations.

A number of factors were identified which influence the determination of red blood cell glucose 6-phosphate dehydrogenase (G6PD). White blood cells were effectively removed from whole blood by filtration, resulting in a mean reduction of G6PD activity of greater than 1.0 U/g Hb. Optimal enzyme activity was found using haemolysates with a Hb concentration in the range 0.4-1.2 g/dl. At a constant temperature of 30 degrees C, maximum linear rate of activity was achieved between the 10th and 20th min after initiation of the reaction. As a result of these findings, modifications to standardize the assay system were introduced. The new method exhibits excellent precision (CV less than 2.0%) with normal samples, and 95% reference ranges of 7.00-11.15 U/g Hb for adult females and 7.05-10.75 U/g Hb for adult males.