What are the common routine iron blood studies for a general adult population?

Common Routine Iron Blood Studies

The standard iron panel for assessing iron status in adults includes serum ferritin, transferrin saturation (TSAT), total iron-binding capacity (TIBC), and serum iron, measured simultaneously for optimal diagnostic accuracy. 1, 2

Core Components of the Iron Panel

Primary Tests (Order These Together)

• Serum Ferritin: Reflects total body iron stores with reference ranges of 20-250 μg/L in men and 20-200 μg/L in women 1

  • Most sensitive single test for iron deficiency when <30 μg/L in the absence of inflammation 3, 4
  • Acts as an acute-phase reactant, so can be falsely elevated during inflammation, infection, or liver disease 1, 4

• Transferrin Saturation (TSAT): Calculated as (serum iron/TIBC) × 100%, with normal range 20-50% 1

  • TSAT <16-20% confirms iron deficiency 2, 3, 4
  • TSAT >45-50% suggests iron overload conditions like hemochromatosis 1, 3
  • Should be measured after overnight fasting to avoid postprandial variation 1, 2

• Total Iron-Binding Capacity (TIBC): Measures transferrin's capacity to bind iron, with normal range 250-370 μg/dL 1

  • Elevated TIBC (>350 μg/dL) indicates iron deficiency as the body produces more transferrin to capture available iron 2, 3
  • Decreased TIBC suggests chronic inflammation, malnutrition, or iron overload 3

• Serum Iron: Measures circulating iron bound to transferrin, with normal range 50-175 μg/dL 1

  • Has significant diurnal variation and is affected by recent meals, making it less reliable as a standalone test 2
  • Low serum iron occurs in both iron deficiency and chronic disease 1

Complementary Hematologic Tests

• Complete Blood Count (CBC) with hemoglobin, hematocrit, mean corpuscular volume (MCV), and red blood cell count 1, 2
  • Hemoglobin <13.5 g/dL (men) or <12.0 g/dL (women) indicates anemia 1
  • MCV <80 fL suggests microcytic anemia, characteristic of iron deficiency 1
  • Critical caveat: Hemoglobin and hematocrit are late indicators that only decrease with severe iron depletion, so normal values do not exclude iron deficiency 1, 5

Diagnostic Interpretation Algorithm

For Iron Deficiency

Strong indication of iron deficiency: TSAT <16% AND TIBC >370 μg/dL AND ferritin <30 μg/L (without inflammation) 2, 3

In the presence of inflammation: Ferritin up to 100 μg/L may still indicate iron deficiency despite appearing "normal" 1, 3, 4

For Iron Overload

Suspicious for hemochromatosis: TSAT >45% AND ferritin >200 μg/L (women) or >300 μg/L (men) 1, 3, 4

For Chronic Disease Anemia

Low serum iron, low-normal or decreased TIBC, normal or elevated ferritin, and low TSAT distinguish anemia of chronic disease from iron deficiency 1, 6

Advanced/Newer Tests (Not Routine, But Available)

• Soluble Transferrin Receptor: Not influenced by inflammation, useful when ferritin interpretation is unclear 1
• Hepcidin: Most precise marker for iron deficiency in inflammatory conditions, but not yet widely available 1
• Reticulocyte Hemoglobin Content: Reflects iron available for erythropoiesis in bone marrow 1
• Unsaturated Iron-Binding Capacity (UIBC): Better diagnostic accuracy (0.80-0.97) than serum iron alone for identifying empty iron stores 2

Critical Testing Considerations

Timing and Sample Collection

• Draw blood in the morning after overnight fasting to minimize diurnal variation and postprandial effects 1, 2, 3
• Day-to-day variation is greater for TSAT than hemoglobin, so repeat testing may be needed if results are borderline 2

Common Pitfalls to Avoid

• Never rely on CBC alone without iron studies, as many iron-deficient patients have normal hemoglobin, hematocrit, and MCV until severe depletion occurs 1, 5
• Do not interpret ferritin in isolation during acute illness, as inflammation falsely elevates levels and masks deficiency 1, 3, 4
• Avoid single-test screening with serum iron or TIBC alone, as these have poor predictive value without the complete panel 1, 6

When Results Are Equivocal

• If ferritin is 30-100 μg/L with unclear clinical picture, measure C-reactive protein to assess for inflammation 2
• Bone marrow biopsy with iron staining remains the gold standard when diagnosis is uncertain and critical for management 1, 3

Special Population Considerations

• Pregnant women: Screen routinely as iron deficiency anemia affects maternal and infant outcomes 1
• Men and postmenopausal women: Iron deficiency anemia is uncommon (<2%), so investigate for gastrointestinal bleeding or chronic disease when present 1
• Chronic kidney disease patients: Use ferritin <100 ng/mL as the threshold for iron deficiency 4