Folate deficiency laboratory findings
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
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Overview
Laboratory Findings
First line investigations include the following:
- Examination of peripheral blood smear : Macrocytic anemia and hypersegmented neutrophils are classically seen in folate deficiency. Anisocytosis and poikilocytosis can also be observed.
- Complete Blood Count : Low hemoglobin, Low hematocrit, elevated MCV and MCH, thrombocytopenia, neutropenia.
- Reticulocyte count :
| Reference Range | |
| Folic Acid in Serum/Plasma Deficiency | 3.6-15 mg/dl |
| Adequate Folic Acid Supply | > 4 ug/l |
| Erythrocyte Folic Acid | 120-800 ug/l |
MCV is often >110. Hematocrit can often be as low as 15. Elevated LDH and bilirubin are seen since dyserythopoesis leads to destruction of >90% of RBC precursors. Hypersegmentation of PMNs is quite sensitive (>5% with 5 or more lobes or >1% with 6 lobes). Reticulocyte, WBC and platelets are low to normal. In one series of patients with B12 deficiency, 64% had a MCV greater than 100, and only 29% had anemia. In general the blood film can point towards vitamin deficiency:
- Complete blood count:
- Decreased hemoglobin and hematocrit levels
- Increased mean corpuscular volume (MCV >95 fl often >110) and mean corpuscular hemoglobin (MCH)
- Low corrected reticulocyte count which indicates decreased production by the bone marrow.
- The platelet count may be reduced.
- Examination of peripheral blood smear :
- Neutrophil granulocytes may show multisegmented nuclei ("senile neutrophil"). This is thought to be due to decreased production and a compensatory prolonged lifespan for circulating neutrophils.
- Anisocytosis (increased variation in RBC size) and poikilocytosis (abnormally shaped RBCs).
- Macrocytes (larger than normal RBCs) are present.
- Ovalocytes (oval shaped RBCs) are present.
- Bone marrow (not normally checked in a patient suspected of megaloblastic anemia) shows megaloblastic hyperplasia.
- Howell-Jolly bodies (chromosomal remnant) also present.
Blood chemistries will also show:
- Increased homocysteine and methylmalonic acid in B12 deficiency
- Increased homocysteine in folate defiency