Erythrocyte creatine levels in anemia.

The automated diacetyl-l-napthol procedure was found to be a simple and relatively quick method for the determination of erythrocyte creatine (EC), exhibiting both better precision and greater sensitivity than reticulocyte counting. A reference range of 1.8 to 5.0 mg per dl (mean, 3.0 +/- 0.9 mg per dl) was established by measuring EC levels in 81 normal adults varying in ages from 20 to 47 years of age. Normal creatine values displayed a slight sex dependency, with females exhibiting somewhat higher levels than males. In evaluating the relative usefulness of EC versus reticulocyte counting in the assessment of anemia, both parameters were measured and compared in 41 patients with various hemolytic and nonhemolytic anemias. A direct relationship was noted between the two parameters (p less than 0.0001); however, the actual data correlation was only fair (r = 0.49). In a serial study of an iron-deficiency anemic patient responding to iron administration, erythrocyte creatine levels were found to rise more slowly than the reticulocyte count and to remain elevated after the reticulocyte count had returned to normal.