Folate, Serum and Erythrocytes (RBCs)

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Subject: Folate, Serum and Erythrocytes (RBCs)

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Definition

  • Folate refers to all derivatives of folic acid. Folate is an essential vitamin present in a wide variety of foods such as dark leafy vegetables, citrus fruits, yeast, beans, eggs, and milk. Folate is vital to normal cell growth and DNA synthesis. A folate deficiency can lead to megaloblastic anemia and ultimately to severe neurologic problems. Folate levels in both serum and RBCs are used to assess folate status. The serum folate level is an indicator of recent folate intake. RBC folate is the best indicator of long-term folate stores. A low RBC folate value may indicate a prolonged folate deficiency. Other names: vitamin B9.

  • Normal range:

    • Serum folate: >6.5 ng/mL

    • RBC folate: 280–903 ng/mL

Use

  • Evaluation of folate deficiency

Interpretation

Increased In

  • Blind loop syndrome

  • Vegetarian diet

  • Distal and small bowel disease

  • PA

Decreased In

  • Untreated folate deficiency, associated with megaloblastic anemia

  • Infantile hyperthyroidism

  • Alcoholism

  • Malnutrition

  • Scurvy

  • Liver disease

  • Vitamin B12 deficiency

  • Dietary amino acid excess

  • Chronic hemodialysis

  • Celiac disease

  • Disorders of glutathione metabolism

  • Sideroblastic anemia

  • Pregnancy

  • Whipple disease

  • Amyloidosis

Limitations

  • Serum folate is a relatively nonspecific test. Low serum folate levels may be seen in the absence of deficiency, and normal levels may be seen in patients with macrocytic anemia, dementia, neuropsychiatric disorders, and pregnancy disorders.

  • Patients with low RBC folate or megaloblastic anemia should be evaluated for vitamin B12 deficiency. To distinguish between vitamin B12 and folate deficiency, determination of homocysteine (HCS) and methylmalonic acid (MMA) will help. In vitamin B12 deficiency, both HCS and MMA are elevated, whereas in folate deficiency, only HCS levels are elevated.

 
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