Hypersegmented Neutrophils and Vitamin B ₁₂ Deficiency

Abstract

The sensitivities and specificities of the mean cell volume (MCV), the red cell distribution width (RDW), and blood smear hypersegmentation for B<sub>12</sub> deficiency were reviewed in 515 patients whose B<sub>12</sub> levels were determined. 61 patients had B<sub>12</sub> levels less than 200 pg/ml. 43 patients were defined as B<sub>12</sub> deficient (n = 13) or non- B<sub>12</sub> deficient (n = 30). Hypersegmentation was more sensitive (91 %) than MCV > 95 fl (62%) or RDW > 15% (54%) in detecting B<sub>12</sub> deficiency. The MCV and the RDW should not be relied on when screening for B<sub>12</sub> deficiency; examination of the blood smear for hypersegmentation is essential.