Clinical significance of a high mean corpuscular volume in nonanemic patients.

A prospective study of the clinical significance of macrocytosis (mean corpuscular volume 100 fL or more) was carried out for 9 months in a teaching hospital in 1975. Of the 140 patients with macrocytosis at the time of admission (0l7% of all hospital admissions) 46 (33%) had low activity of serum or erythrocyte folate, or both, and 16 (11%) had low serum vitamin B12 concentrations. Among the 78 patients with normal B12 and folate values the most commonly associated significant clinical conditions were alcoholism or hepatic disease (36 patients), malignant disease or the effects of chemotherapy (25 patients) and chronic obstructive lung disease (10 patients).