Folate deficiency in an unselected population in Calgary, Alberta and its relationship with red blood cell macrocytosis.

BACKGROUND: Folate deficiency is rare in western countries and therefore blood tests for folate level have limited indications. One such indication is red cell macrocytosis, however it is unclear if the association of macrocytosis with folate deficiency is robust enough to serve as a risk marker. Our objective is to determine whether macrocytosis is a useful marker for folate deficiency.

FINDINGS: Paired data from the Calgary Laboratory Services Information System was analyzed using receiver operating characteristic (ROC) curves to determine strength of association between mean corpuscular volume and serum folate. Strength of association was analyzed for serum folate cut-off values of 12, 10, 8, and 6 nmol/L. Overall, 0.2% of individuals were folate deficient (<6 nmol/L serum folate). Based on ROC curves, at each cut-off level, mean corpuscular volume was a poor predictive marker for serum folate level.

CONCLUSIONS: Folate deficiency is rare in Calgary, Alberta. Macrocytosis is not a strong predictor for folate deficiency.