What is the interpretation of the laboratory findings showing mild normocytic anemia with low hemoglobin and hematocrit, normal white blood cell and platelet counts, normal renal function, low transferrin saturation, normal iron, normal total iron‑binding capacity, normal ferritin, normal haptoglobin, normal lactate dehydrogenase, normal erythropoietin, no hemoglobin variant, and negative autoimmune markers?

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Last updated: October 28, 2026 • View editorial policy

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Interpretation: Functional Iron Deficiency Without Absolute Iron Depletion

These laboratory findings indicate functional iron deficiency (FID) despite normal ferritin levels, characterized by inadequate iron availability for erythropoiesis in the setting of borderline-low transferrin saturation (28%) and a notably low soluble transferrin receptor (sTfR 0.52 L). This pattern does not fit classic iron deficiency anemia, hemolysis, or autoimmune disease.

Key Diagnostic Findings

Iron Studies Pattern

  • Transferrin saturation of 28% sits at the borderline threshold (normal typically >20-30%), suggesting marginal iron availability for red cell production 11
  • Ferritin 115 μg/L is well above the iron deficiency threshold (<45 μg/L in anemia, <15 μg/L for absolute deficiency) 21
  • Low sTfR (0.52 L) is paradoxical—this should be elevated in true iron deficiency, indicating this is NOT classic iron deficiency anemia 3
  • Normal TIBC (274) and serum iron (78) further argue against absolute iron depletion

Hemolysis Ruled Out

  • Normal LDH (131), normal haptoglobin (150), and no hemoglobin variants effectively exclude hemolytic anemia 4
  • Normal reticulocyte response would be expected if checked

Inflammation and Autoimmune Excluded

  • CRP <3.0 and ESR 14 rule out significant inflammatory process
  • Negative ANA, RF, Sjögren's antibodies, and normal complement exclude autoimmune causes 11

Erythropoietin Response

  • EPO 14.0 is inappropriately normal-to-low for the degree of anemia (Hb 12.8 in what appears to be a female patient based on reference ranges)
  • This suggests either early chronic kidney disease effect (Cr 1.20 is borderline elevated) or relative EPO insufficiency 14

Clinical Interpretation

This represents early functional iron deficiency or anemia of chronic disease (ACD) in evolution, where:

  1. Iron availability is marginal (transferrin saturation 28%) but stores remain adequate (ferritin 115)
  2. The low sTfR paradoxically suggests decreased erythropoietic drive rather than iron-starved erythropoiesis—this can occur in early ACD or when EPO response is blunted 3
  3. Borderline renal function (Cr 1.20) may contribute to relative EPO insufficiency, though not yet at the threshold where CKD typically causes significant anemia (GFR likely >45-60) 1

Critical Caveat

The low sTfR is the most puzzling finding. In typical iron deficiency, sTfR should be elevated as erythroid precursors upregulate transferrin receptors seeking iron 35. A low value suggests either:

  • Laboratory error or assay variability (sTfR assays are not standardized)
  • Suppressed erythropoiesis from another cause
  • Very early stage where compensatory mechanisms haven't fully activated

Recommended Next Steps

Immediate Actions

  1. Repeat sTfR measurement to confirm the low value—this is atypical and may represent lab error
  2. Calculate sTfR/log ferritin index: Even with low sTfR, this ratio helps distinguish functional ID from ACD 3. With ferritin 115, log ferritin = 2.06, so index = 0.52/2.06 = 0.25 (very low, suggesting ACD pattern rather than ID)
  3. Check reticulocyte count and reticulocyte hemoglobin content (CHr) if available—CHr <28 pg indicates functional iron deficiency regardless of ferritin 3

Clinical Evaluation

  • Assess for occult blood loss: Even with normal ferritin, GI evaluation should be considered in men or postmenopausal women with any degree of anemia 11
  • Evaluate renal function more thoroughly: Calculate GFR; if <60 mL/min/1.73m², CKD may be contributing 1
  • Review medications: NSAIDs, anticoagulants, or antiplatelet agents may cause occult GI blood loss
  • Dietary assessment: Inadequate iron intake can cause functional deficiency even with adequate stores

Management Approach

  • Do NOT start empiric iron supplementation yet—ferritin 115 and transferrin saturation 28% do not meet criteria for iron replacement 21
  • If CHr is low (<28 pg) or repeat testing confirms functional ID: Trial of oral iron supplementation (ferrous sulfate 325 mg daily on empty stomach) may be reasonable 2
  • If GFR <45 and anemia worsens: Consider nephrology referral for EPO evaluation 1
  • Monitor hemoglobin in 8-12 weeks: Stability suggests observation; decline warrants investigation for occult blood loss or progression to true iron deficiency

What This Is NOT

  • Not classic iron deficiency anemia: Ferritin too high, sTfR too low
  • Not hemolytic anemia: Normal LDH, haptoglobin, no variants
  • Not autoimmune/inflammatory: Negative serologies, normal inflammatory markers
  • Not yet significant CKD anemia: Cr only borderline elevated, EPO not severely suppressed

The most likely diagnosis is early functional iron deficiency or evolving anemia of chronic disease with borderline renal function as a potential contributor, but the atypical sTfR requires confirmation before definitive categorization.

References

4
Research

Anemia: Normocytic Anemia.

FP essentials, 2023

5
Research

Diagnosing iron deficiency: Controversies and novel metrics.

Best practice & research. Clinical anaesthesiology, 2023

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