Diminished need for folate measurements among indigent populations in the post folic acid supplementation era.

Context: The mandated fortification of processed grains with folic acid in the United States and Canada in 1998 was intended to reduce the incidence of neural tube defects in pregnant women. The incidence of folate deficiency in most populations has declined dramatically since then.

Objective: To determine the rate of folate deficiency in a cohort of indigent patients, a population among those at highest risk for folate deficiency.

Design: Using data from 3 years (1997, 2000, and 2004), we examined results of laboratory tests for red blood cell folate ordered at 3 hospitals that predominately service the needs of indigent patients. Folate concentration cutoffs were 160 ng/mL (363.6 nmol/L) and 94 ng/mL (213 nmol/L).

Results: Using a red blood cell folate cutoff concentration of 160 ng/mL (363.6 nmol/L), the combined incidence of folate deficiency decreased from 4.8% in 1997 to 0.6% in 2004. At a cutoff of 94 ng/mL (213 nmol/L), the incidence went from 0.98% to 0.09% in 1997 and 2004, respectively. Even when the folate concentration was found to be low, the majority of these subjects did not have macrocytosis.

Conclusions: These data suggest that folate deficiency has become a rare event in the United States, and the utility of routine folate measurements for patients with anemia and/or increased mean corpuscular volume are difficult to justify.