Serum Vitamin B12 Levels
Serum Vitamin B12 Levels
Serum vitamin B12 (cobalamin) measurement is a crucial diagnostic test for assessing vitamin B12 status in pediatric patients. This test quantifies both active and inactive forms of vitamin B12 in the blood.
Key Points:
- Essential for neurological development
- Critical for DNA synthesis and red blood cell formation
- Deficiency can cause irreversible neurological damage
- Primary screening test for B12 deficiency
Clinical Significance
Indications for Testing:
- Unexplained anemia or macrocytosis
- Developmental delay or regression
- Neurological symptoms
- Failure to thrive
- Vegetarian/vegan diet
- Maternal B12 deficiency
Clinical Presentations:
- Megaloblastic anemia
- Irritability
- Developmental regression
- Seizures
- Hypotonia
- Growth failure
Sample Collection and Processing
Collection Requirements:
- Fasting sample preferred (4-8 hours)
- Serum separator tube (SST)
- Protect from light
- Volume: Minimum 0.5 mL serum
Pre-analytical Factors:
- Avoid hemolysis
- Process within 2 hours
- Store at 2-8°C if delayed processing
- Avoid recent vitamin B12 supplementation
Pediatric Reference Ranges
Age-Specific Values:
Newborns (0-30 days): 200-1000 pg/mL
Infants (1-12 months): 200-900 pg/mL
Children (1-18 years): 200-900 pg/mL
Interpretative Guidelines:
- Severe deficiency: <100 pg/mL
- Moderate deficiency: 100-200 pg/mL
- Borderline: 200-300 pg/mL
- Normal: 300-900 pg/mL
- High: >900 pg/mL
Result Interpretation
Low Vitamin B12 Causes:
- Dietary deficiency
- Malabsorption disorders
- Maternal deficiency (breastfed infants)
- Genetic disorders of B12 metabolism
- Inflammatory bowel disease
- Celiac disease
High Vitamin B12 Causes:
- Recent B12 supplementation
- Liver disease
- Myeloproliferative disorders
- Genetic polymorphisms
Test Limitations and Considerations
Important Considerations:
- May not reflect tissue B12 status
- Can be normal in early deficiency
- Affected by recent supplementation
- Consider concurrent methylmalonic acid testing
- False elevations in liver disease
Interfering Factors:
- Folate deficiency
- Recent transfusion
- Antibiotics
- Oral contraceptives
- Hemolysis
