In a 9‑year‑old child with elevated total iron‑binding capacity, low transferrin saturation, and normal ferritin, are these findings still consistent with iron deficiency?

Yes, These Findings Are Consistent with Iron Deficiency Despite Normal Ferritin

In a 9-year-old child with elevated TIBC, low transferrin saturation, and normal ferritin, these results definitively indicate iron deficiency—specifically early-stage or latent iron deficiency where iron stores are being mobilized but not yet depleted. 1, 2

Understanding the Laboratory Pattern

The combination of elevated TIBC with low transferrin saturation is diagnostic of iron deficiency, regardless of ferritin level. 1, 2 This pattern reflects a critical physiologic sequence:

• Elevated TIBC occurs as a compensatory mechanism before serum iron drops, representing the body's attempt to maximize iron-binding capacity and mobilize all available tissue iron to maintain normal erythropoiesis. 2
• Low transferrin saturation (<16% in adults, similar threshold in children) confirms that transferrin has a high proportion of vacant iron-binding sites, indicating insufficient circulating iron for red blood cell production. 1, 3
• Normal ferritin in this context does not exclude iron deficiency—it simply means iron stores have not yet been completely exhausted. 1

Why Normal Ferritin Does Not Rule Out Iron Deficiency

The ferritin test detects iron deficiency in many cases where serum iron and TIBC patterns are not yet classically abnormal, but the reverse is also true: elevated TIBC can detect early iron deficiency before ferritin falls. 4, 2

• During the development of iron deficiency, TIBC elevation precedes the decrease in serum iron and the depletion of ferritin stores. 2
• Studies demonstrate that normal serum iron with elevated TIBC and normal transferrin saturation can coexist with depleted bone marrow iron stores, confirming that this laboratory pattern represents true iron deficiency. 2
• Ferritin is less sensitive than TIBC for detecting early or latent iron deficiency, particularly in children where iron demands are high due to growth. 4, 5

Clinical Interpretation Algorithm

Step 1 – Confirm iron-deficient erythropoiesis:

• Low transferrin saturation (<16–20%) with elevated TIBC unequivocally confirms that the bone marrow lacks sufficient available iron for hemoglobin synthesis. 1, 3

Step 2 – Classify the stage of iron deficiency:

• Normal ferritin + elevated TIBC + low TSAT = early/latent iron deficiency with ongoing mobilization of iron stores but not yet complete depletion. 2
• This represents a compensatory phase where the body is attempting to maintain erythropoiesis by increasing transferrin production. 2

Step 3 – Identify the underlying cause in a 9-year-old:

• Dietary insufficiency (inadequate iron intake, restrictive diets, excessive milk consumption displacing iron-rich foods). 1
• Rapid growth spurts increasing iron demands beyond dietary intake. 1
• Occult gastrointestinal blood loss (Meckel's diverticulum, inflammatory bowel disease, celiac disease, parasitic infections). 1
• Malabsorption disorders (celiac disease is particularly common and often presents with isolated iron deficiency before other symptoms). 1

Common Diagnostic Pitfalls to Avoid

• Do not dismiss iron deficiency based solely on "normal" ferritin—ferritin lags behind TIBC elevation in the evolution of iron deficiency. 1, 2
• Do not rely on serum iron alone, as it has high day-to-day variability and is affected by recent meals, diurnal variation, and inflammation. 1, 4
• Recognize that children with normal hemoglobin can still have iron deficiency—hemoglobin screening alone misses over 50% of iron deficiency cases in modern populations. 3

Treatment and Monitoring

Initiate oral iron supplementation (elemental iron 3–6 mg/kg/day in divided doses) and investigate the underlying cause. 1

• Expect hemoglobin to rise by 1–2 g/dL within 4–8 weeks if the diagnosis is correct and compliance is adequate. 3
• Recheck iron parameters (including ferritin) after 3 months of therapy to confirm repletion and ensure ferritin rises to ≥30 ng/mL with TSAT ≥20%. 1, 3
• If no response occurs, consider malabsorption (celiac disease, inflammatory bowel disease) or ongoing blood loss requiring gastrointestinal evaluation. 1