Anemia and macrocytosis in the prediction of serum folate and vitamin B12 status, and treatment outcome in major depression.

Background: Folate and B12 deficiencies may result in macrocytic anemia, and are common in major depression; hypofolatemia may result in poorer antidepressant response. We wished to determine whether anemia or macrocytosis predict hypofolatemia, low B12, or refractoriness to antidepressants.

Methods: After obtaining serum folate, B12, and hematological indices, 213 depressed adults were treated with fluoxetine 20 mg/day. Amelioration of depressive symptoms was measured.

Results: Neither macrocytosis nor anemia predicted low serum folate/B12, or antidepressant refractoriness. Among 39 patients with hypofolatemia, none had macrocytosis; 28% had low HCT; 41% had low RBC. Among 25 patients with low B12, none had macrocytosis; 24% had low HCT; 28% had low RBC. Among non-responders, 3% had macrocytosis; 24% had low HCT; 25% had low RBC.

Conclusion: Anemia and macrocytosis should not be used to predict folate or B12 deficiencies, or refractoriness to antidepressants. Measurement of folate and B12 should be considered when evaluating treatment refractoriness.