Demonstration of vitamin B12 deficiency by a simple cytochemical reaction in the peripheral blood smear.

A simple, rapid and inexpensive cytochemical method for the detection of vitamin B 12 deficiency was applied in several types of anemias and matched with the levels of vitamin B12 and folic acid in the serum of the patients. It was found that in patients with low vitamin B12 levels the stained erythrocytes and the erythroid precursors showed a yellowish brown discoloration, which was not detected in folic acid deficiency and all other types of anemias. This test therefore may be used for differentiation between B12 and folate deficiency whenever megaloblastic anemia is diagnosed.