Transferrin Saturation (TSAT)
Key Points
- Essential marker of iron availability for erythropoiesis
- Calculated from serum iron and total iron-binding capacity (TIBC)
- Formula: TSAT = (Serum Iron ÷ TIBC) × 100
- Critical for diagnosing iron disorders in children
- Dynamic marker reflecting recent iron status
Physiology & Metabolism
Transferrin Function
- Primary iron transport protein in plasma
- Binds two Fe³⁺ ions per molecule
- Regulated by iron regulatory proteins (IRPs)
- Essential for cellular iron uptake
Regulatory Mechanisms
- Hormonal Control
- Hepcidin regulation
- Inflammatory cytokines
- Growth factors
- Cellular Regulation
- Transferrin receptor expression
- Iron regulatory elements
- Cellular iron sensors
Clinical Utility
Primary Applications
- Diagnosis of Iron Deficiency
- Early detection before anemia develops
- Monitoring of high-risk populations
- Assessment of treatment response
- Iron Overload Evaluation
- Hereditary hemochromatosis screening
- Transfusion-related iron overload
- Secondary hemochromatosis
Disease Associations
- Low TSAT (<20%)
- Iron deficiency anemia
- Anemia of chronic disease
- Chronic kidney disease
- High TSAT (>45%)
- Hemochromatosis
- Transfusional iron overload
- Acute liver injury
Methodology
Sample Collection
- Timing Considerations
- Morning collection preferred
- Fasting state recommended
- Avoid recent iron supplementation
- Processing Requirements
- Serum separator tubes
- Prompt separation
- Temperature control
Analytical Methods
- Serum Iron Measurement
- Colorimetric methods
- Atomic absorption spectroscopy
- Quality control considerations
- TIBC Determination
- Direct measurement
- Calculated from transferrin
- Standardization protocols
Result Interpretation
Reference Ranges by Age
- Newborns: 35-85%
- Infants (1-12 months): 25-40%
- Children (1-12 years): 20-40%
- Adolescents: 15-45%
Interpretation Factors
- Diurnal Variation
- Morning peak
- Evening nadir
- Impact on reference ranges
- Physiologic Influences
- Growth spurts
- Menstruation onset
- Nutritional status
Common Pitfalls
- Pre-analytical variables
- Acute phase response effects
- Recent iron therapy impact
- Inflammatory conditions
Pediatric Considerations
Age-Specific Challenges
- Developmental Changes
- Iron requirements during growth
- Physiologic variations
- Impact of puberty
- Special Populations
- Premature infants
- Athletes
- Chronic disease states
Monitoring Considerations
- Frequency of Testing
- Risk-based screening
- Treatment monitoring
- Follow-up protocols
- Integration with Other Tests
- Complete blood count
- Ferritin levels
- Iron studies panel
Clinical Scenarios
Common Presentations
- Iron Deficiency Investigation
- Poor growth
- Fatigue
- Developmental concerns
- Chronic Disease Monitoring
- Inflammatory bowel disease
- Chronic kidney disease
- Malignancies
Further Reading
