This test measures the concentration of soluble transferrin receptors released by cells when iron demand increases.
Diagnostic Value: sTfR helps distinguish between iron-deficiency anemia and anemia of chronic disease.
Clinical Significance: Elevated sTfR indicates tissue-level iron deficiency even when ferritin levels appear normal.
Symptom Correlation: May correlate with weakness, pallor, or poor exercise tolerance.
The sTfR test provides a sensitive marker for early iron depletion.