Iron Studies Interpretation: Iron Deficiency
Your results indicate iron deficiency, characterized by low serum iron (7.8 μmol/L), low transferrin saturation (14%), and a TIBC (54 μmol/L) that suggests your body is attempting to compensate by producing more transferrin to capture available iron.
Understanding Your Results
Your transferrin saturation of 14% is below the critical threshold of 16%, which is a sensitive marker for iron deficiency, though it has relatively low specificity (40-50%) 1. This low TSAT reflects insufficient iron readily available for red blood cell production 1.
The pattern you present—low serum iron combined with low transferrin saturation—indicates that iron delivery to your bone marrow for hemoglobin synthesis is impaired 1.
Critical Missing Information
You need a serum ferritin level to complete this assessment. Without ferritin, I cannot definitively distinguish between:
- Absolute iron deficiency (depleted iron stores): ferritin <15-30 μg/L 1, 2
- Functional iron deficiency (adequate stores but impaired release): ferritin 30-100 μg/L with inflammation 1
- Anemia of chronic disease (inflammatory iron block): ferritin >100 μg/L with TSAT <16% 1
Ferritin is the most specific indicator of depleted iron stores available, with levels <15 μg/L having 99% specificity for iron deficiency 2. However, ferritin is an acute-phase reactant that rises during inflammation, infection, or tissue damage, potentially masking true iron deficiency 1, 2.
Next Steps for Diagnosis
Immediate Laboratory Testing Needed:
- Serum ferritin (essential for diagnosis) 1, 2
- Complete blood count with hemoglobin/hematocrit and red cell indices (MCV, MCH, MCHC) 1, 3
- Inflammatory markers (CRP or ESR) to interpret ferritin accurately 1
Interpretation Algorithm Based on Ferritin Results:
If ferritin <15 μg/L: Absolute iron deficiency confirmed 1, 2
- Investigate the source of iron loss (gastrointestinal bleeding most common in men and non-menstruating women) 3, 4
- Stool guaiac testing for occult blood 1
- Consider gastrointestinal endoscopy if indicated 3
If ferritin 15-30 μg/L: Likely iron deficiency with low stores 2
- Proceed with iron supplementation
- Monitor response to therapy
If ferritin 30-100 μg/L with elevated CRP/ESR: Mixed picture—combination of true iron deficiency and anemia of chronic disease 1
- Address underlying inflammatory condition
- Consider iron supplementation
If ferritin >100 μg/L with elevated CRP/ESR: Anemia of chronic disease (inflammatory iron block) 1
- Treat underlying inflammatory condition as primary intervention
- Iron supplementation less likely to be effective
Common Pitfalls to Avoid
Do not diagnose or treat based on transferrin saturation alone. TSAT <20% does not perfectly discriminate between patients who are truly iron deficient versus those with functional deficiency or inflammation 1.
Do not assume normal hemoglobin excludes iron deficiency. Iron deficiency without anemia (normal hemoglobin but low ferritin) is common and can still cause symptoms like fatigue and reduced exercise tolerance 1, 2.
Do not order ferritin without checking inflammatory markers. Ferritin interpretation requires knowledge of inflammatory status, as inflammation can elevate ferritin levels independently of iron stores 1.
Do not rely on a single test. Hemoglobin and hematocrit alone are unreliable for detecting early iron deficiency, as they decrease only with severe depletion 5.
Clinical Significance
Even without anemia, iron deficiency can cause:
- Fatigue and lethargy 6
- Reduced aerobic performance and exercise intolerance 1
- Poor concentration 6
- In children, neurodevelopmental deficits 6
The most common cause of iron deficiency in adults is blood loss, typically from the gastrointestinal tract in men and postmenopausal women, or menstruation in premenopausal women 3, 4.
Human iron metabolism is a conservation-based system, so iron deficiency usually indicates loss of normal iron conservation mechanisms 4.