Blood count and hematologic morphology in nonanemic macrocytosis: differences between alcohol abuse and pernicious anemia.

In order to find out if blood count parameters could help to differentiate between the two most common causes for nonanemic macrocytosis, alcohol abuse and vitamin B12 deficiency, we studied 18 nonanemic pernicious anemia patients and 136 alcohol abusers without deficiency of folate and with an erythrocyte mean cell volume (MCV) value > or = 100 femtoliters. In addition to blood count reticulocytes, peripheral blood smear and marrow aspirates were examined. The combination of a low red cell count (< 4.0 x 10(12)/l) or a high red cell distribution width (E-CDW) value (> 15.0%) with a normal thrombocyte count and a normal thrombocyte mean cell volume (T-MCV) was found in 94.4% of the vitamin deficient patients but in only 14.6% of the abusers, in 25.0% of the folate deficient patients (n = 8), and in 26.9% of the patients without any cause for macrocytosis (n = 52). None of the peripheral blood smear or marrow findings exceeded this sensitivity, and the few highly specific findings had low sensitivities. Thus, the combination of the four blood count parameters proved to be, as compared to hematologic morphology, a good diagnostic tool in selecting patients for appropriate further diagnostic tests. All patients with macrocytosis should be asked about their alcohol consumption. Additionally, serum B12 vitamin should be measured at least when nonanemic macrocytosis is combined to a low red cell count or a high E-CDW and the thrombocyte count and T-MCV are normal.