Of what value are folate levels?

As a geriatrician, I often order serum folate levels as part of a workup for dementia or anemia. How accurate is the statement that “serum folate levels are not useful because they fluctuate rapidly with dietary intake and are not cost-effective” (Am Fam Physician. 2009;79:203-208), which, I believe, is based on an earlier article that discussed anemic but not demented patients (Am J Med. 2001;110:88-90). All my colleagues and I continue to check patients' vitamin B12 and folate levels daily. Is this no longer the recommended standard? Should we be checking RBC folate levels instead?
—Steven M. Schwartz, MD, Bronx, N.Y.

The available evidence does not support routine testing for folate deficiency in the workup of dementia. Since the 1998 FDA-mandated fortification of grain products, the prevalence of folate deficiency has decreased markedly, even among high-risk patients. A recent study found that low folate levels were rarely (0.4%) detected in a series of patients being evaluated for anemia, dementia, or altered mental status and occurred primarily in patients with macrocytic anemia (J Gen Intern Med. 2008;23:824-826). The authors concluded that folate deficiency was rare “in the era of fortification of the American diet” and that folic acid testing should be “reserved for those with macrocytic anemia and those at high risk for folic acid deficiency,” such as patients with alcohol abuse, malnutrition, or malabsorption and those receiving chemotherapy.

The 2001 Practice Parameter from the American Academy of Neurology for the workup of dementia no longer includes testing for folic acid deficiency whereas the 1994 recommendations did. The current recommendations state that the available evidence supports screening for comorbid depression, B12 deficiency, and hypothyroidism, with testing for syphilis reserved for patients who have a specific risk factor or evidence of prior syphilitic infection (Neurology. 2001;56:1143-1153).
—Susan Kashaf, MD, MPH
(127-4)
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