Detection of G6PD and pyruvate kinase deficiencies in reticulocytosis by reference to erythrocyte creatine.

Erythrocyte activities of G6PD and PK, referenced to creatine content, are presented as a means to detect enzyme deficiencies despite the presence of variable proportions of young erythrocytes in the assayed cell population. Lysate enzyme activities, creatine and hemoglobin concentrations, and whole blood reticulocyte counts were determined on 110 samples from 87 patients with a variety of anemias, including two pyruvate kinase deficient, three G6PD deficient, and four proven G6PD heterozygotes. Highest correlations were obtained between log of G6PD activity/g hemoglobin and lysate creatine, and between PK activity/g hemoglobin and lysate creatine. Ninety-five percent limits for this population are presented for creatine concentrations to 28 mg/dl, corresponding to 20% reticulocyte count. In addition to providing reference intervals appropriate to the suspect patient population, the data afford greater confidence in detecting partial enzyme deficiencies concomitant with other hemolytic processes, such as hemoglobinopathies.