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Lab Test: Folate, RBC Level

    Lab Test
    • Folate (RBC level)
    Description
    • Measurement of folic acid (folate) levels in red blood cells for the evaluation and management of certain anemias or neurologic dysfunction.
    Reference Range
    • Adults:  150-450 ng/mL/cells (340-1020 nmol/L/cells)
    • Children, 2 to 16 years (competitive protein binding radioassay): >160 ng/mL (>362 nmol/L)
    • Adolescents, older than 16 years (competitive protein binding radioassay):  140-628 ng/mL (317-1422 nmol/L)
    Indications & Uses
    • Screening for pregnancy risk of fetal neural tube defect - a decreased level of RBC folic acid may indicate an increased risk of a woman having a child with a neural tube defect, though some data suggests there is no correlation. 
    • Suspected folic acid (folate) deficiency - RBC folate has testing limitations because of sensitivity and specificity issues.  Only about 70% of pregnant women and alcoholics with megaloblastic erythropoiesis thought to be due to folate deficiency have low RBC folate levels, while approximately 20% to 30% of pregnant women and alcoholics had low RBC folate levels in the absence of megaloblastic erythropoiesis.
    Clinical Application

    There is controversy over whether RBC folate is a better test than or comparable to serum folate for the diagnosis of folate deficiency.

    RBC folate levels, unlike serum folate levels, are not affected by recent dietary intake or drugs.

    Test Tube Needed
    • EDTA (competitive protein binding radioassay or automated chemiluminescence)
    • Heparinized tube (automated chemiluminescence)
    Procedure
    • Collect whole blood
    Storage and Handling
    • Specimen stable for 4 hours at 8°C and 8 weeks at -20°C
    References
    • LaGow B et al., eds. PDR Lab Advisor. A Comprehensive Point-of-Care Guide for Over 600 Lab Tests.  First ed. Montvale, NJ: Thomson PDR; 2007.

MESH Terms & Keywords

  • Folate, RBC Level