RBC Folate Levels
Introduction
- Essential B-vitamin (B9) crucial for DNA synthesis and cell division
- Better indicator of long-term folate status than serum folate
- Reflects folate status over RBC lifespan (120 days)
- Critical for neural tube development and hematopoiesis
Key Functions
- One-carbon metabolism
- Purine and pyrimidine synthesis
- Amino acid metabolism
- DNA methylation
- Red blood cell maturation
Biochemistry & Metabolism
Folate Forms
- Dietary Forms:
- Food folate (polyglutamates)
- Folic acid (synthetic)
- 5-methyltetrahydrofolate (active form)
- Metabolic Pathways:
- Absorption in proximal jejunum
- Conversion to tetrahydrofolate
- Integration into one-carbon metabolism
- Storage in RBCs and liver
Metabolic Interactions
- Vitamin B12 dependency
- Homocysteine metabolism
- Methionine synthesis
- SAM-dependent methylation reactions
Testing Methodology
Sample Collection
- Specimen Requirements:
- EDTA whole blood
- Fasting preferred
- Protection from light
- Temperature control
- Pre-analytical Factors:
- Dietary intake
- Medication interference
- Sample stability
- Processing time
Analytical Methods
- Competitive protein binding assay
- Microbiological assay
- Chemiluminescent immunoassay
- LC-MS/MS (gold standard)
Clinical Interpretation
Reference Ranges
- Age-Specific Values:
- Neonates: 320-1200 ng/mL
- Infants: 300-1100 ng/mL
- Children: 280-1000 ng/mL
- Adolescents: 250-900 ng/mL
- Clinical States:
- Deficiency: <200 ng/mL
- Borderline: 200-250 ng/mL
- Normal: >250 ng/mL
- High: >1000 ng/mL
Clinical Scenarios
- Indications for Testing:
- Macrocytic anemia
- Developmental delay
- Neurological symptoms
- Malabsorption evaluation
- Pregnancy planning
- Risk Factors for Deficiency:
- Poor dietary intake
- Malabsorption disorders
- Anticonvulsant therapy
- Chronic hemolysis
Therapeutic Implications
Treatment Guidelines
- Supplementation Protocols:
- Prophylactic dosing: 400-800 mcg/day
- Therapeutic dosing: 1-5 mg/day
- Neural tube defect prevention: 4 mg/day
- Duration based on clinical response
- Monitoring Parameters:
- RBC folate levels
- Complete blood count
- Homocysteine levels
- Clinical response
Special Populations
- Pregnancy:
- Pre-conception requirements
- First trimester dosing
- High-risk cases
- Chronic Diseases:
- Celiac disease
- Inflammatory bowel disease
- Chronic hemolytic anemias
- Malignancies
- Drug Interactions:
- Anticonvulsants
- Methotrexate
- Sulfasalazine
- Trimethoprim
Further Reading
