What does iron studies include?

Iron Studies Components

Iron studies include serum ferritin, serum iron, total iron binding capacity (TIBC), and transferrin saturation as the core components for assessing iron status. 1, 2

Core Components of Iron Studies

• Serum ferritin: The most sensitive test for iron stores; levels <25 ng/ml in males and <11 ng/ml in females indicate insufficient iron stores 1
• Serum iron: Measures circulating iron bound to transferrin 2
• Total iron binding capacity (TIBC): Measures transferrin's capacity to bind iron; elevated in iron deficiency 2
• Transferrin saturation: Calculated as (serum iron × 100)/TIBC; reflects iron immediately available for hemoglobin synthesis; values <20% suggest iron deficiency 2

Interpretation Guidelines

• Transferrin saturation >55% and serum ferritin >200 ng/ml (women) or >300 ng/ml (men) suggest iron overload 3
• In iron deficiency, typically see:
  • Low serum ferritin (<30 ng/mL in those without inflammation) 4
  • Low transferrin saturation (<20%) 2
  • Elevated TIBC 2
  • Low serum iron 2

Clinical Considerations

• Serum ferritin is an acute phase reactant and may be falsely elevated in inflammatory conditions 3, 1
• For patients with chronic inflammatory conditions, a higher ferritin threshold (<100 μg/L) should be used to diagnose iron deficiency 1
• Transferrin or TIBC measurement alone outperforms iron measurement and saturation indices in predicting iron deficiency 5

Special Populations

• In chronic kidney disease patients, ferritin values <100 ng/mL suggest iron deficiency 2
• In pregnancy, different thresholds may apply due to physiological changes 4
• For restless legs syndrome, iron studies should be tested regularly with supplementation considered when ferritin ≤75 ng/mL or transferrin saturation <20% 3

Pitfalls to Avoid

• Relying solely on hemoglobin and hematocrit for iron status assessment, as they are late indicators of iron deficiency 1
• Failing to consider inflammation when interpreting ferritin levels 1
• Not recognizing that serum ferritin levels can have wide variability when measured serially 3
• Assuming that serum iron studies alone can detect specific organ iron overload such as cardiac iron 3

Advanced Testing

• In cases where standard iron studies are inconclusive, additional tests may include:
  • Erythrocyte protoporphyrin concentration 1
  • Percent hypochromic red blood cells (requires specialized equipment) 1
  • MRI for liver iron content (gold standard for non-invasive assessment of iron overload) 2

Iron studies are essential for diagnosing both iron deficiency and iron overload, with the combination of tests providing more accurate assessment than any single measurement alone 1, 2.