Serum Transferrin Receptor (sTfR)
Key Points
- Sensitive marker of tissue iron status
- Independent of inflammation status
- Reflects erythropoietic activity
- Valuable in pediatric iron deficiency assessment
- Superior differentiation of iron deficiency anemia from anemia of chronic disease
Biochemistry & Regulation
Molecular Structure
- Transmembrane glycoprotein
- Composed of:
- Extracellular domain (proteolytically cleaved form found in serum)
- Transmembrane domain
- Cytoplasmic domain
- Molecular weight: 85 kDa (soluble form)
Regulatory Mechanisms
- Transcriptional Control
- Iron-responsive elements (IREs)
- Hypoxia-inducible factors (HIFs)
- Erythropoietin influence
- Post-translational Regulation
- Proteolytic cleavage
- Membrane trafficking
- Receptor recycling
Clinical Utility
Primary Applications
- Differential Diagnosis
- Iron deficiency anemia vs. anemia of chronic disease
- Mixed anemia states
- Early iron deficiency detection
- Monitoring Functions
- Response to iron therapy
- Erythropoiesis assessment
- Iron status in chronic conditions
Specific Clinical Scenarios
- Chronic Kidney Disease
- Monitoring erythropoiesis-stimulating agent therapy
- Iron supplementation guidance
- Inflammatory Conditions
- Assessment when ferritin is unreliable
- Monitoring during immunotherapy
- Athletic Performance
- Sports anemia evaluation
- Training impact assessment
Testing Methods
Sample Collection
- Specimen Requirements
- Serum or plasma
- Fasting not required
- Stable at room temperature for 24 hours
- Processing Guidelines
- Centrifugation within 2 hours
- Storage at -20°C for long-term
- Avoid repeated freeze-thaw cycles
Analytical Methods
- Immunoassay Techniques
- ELISA
- Immunoturbidimetry
- Nephelometry
- Quality Control
- Internal standards
- Method calibration
- Inter-laboratory standardization
Result Interpretation
Reference Ranges
- Age-Specific Values
- Neonates: 2.2-4.5 mg/L
- Infants (1-12 months): 1.8-4.6 mg/L
- Children (1-16 years): 1.4-3.8 mg/L
- Clinical Decision Points
- Iron deficiency: >8.5 mg/L
- Normal range: 2.8-8.5 mg/L
- Functional iron deficiency: >5 mg/L with normal ferritin
Interpretation Factors
- Biological Variables
- Growth velocity
- Erythropoietic activity
- Exercise status
- Mathematical Indices
- sTfR/log ferritin ratio
- sTfR/ferritin index
- Thomas plot analysis
Pediatric Specifics
Developmental Considerations
- Age-Related Changes
- Impact of growth spurts
- Pubertal changes
- Nutritional influences
- Special Populations
- Premature infants
- Adolescent athletes
- Chronic disease states
Clinical Applications
- Screening Protocols
- High-risk populations
- Growth monitoring
- Athletic participation
- Treatment Monitoring
- Iron supplementation
- Nutritional interventions
- Chronic disease management
Advanced Applications
Research Applications
- Population Studies
- Epidemiological surveys
- Nutritional assessments
- Health screening programs
- Clinical Research
- Biomarker development
- Treatment optimization
- Outcome prediction
Further Reading
