Is an iron saturation of 23% within the normal range?

Iron Saturation of 23%: Interpretation and Clinical Significance

An iron saturation (TSAT) of 23% is within the normal range and generally adequate for most patients, though optimal targets may vary depending on clinical context, particularly in those with chronic kidney disease. 1

Normal Range and Interpretation

• A transferrin saturation (TSAT) of 23% exceeds the minimum threshold of 20% that is typically used to define adequate iron availability for erythropoiesis in most clinical scenarios 2
• For the general population without chronic conditions, TSAT values between 20-50% are generally considered normal 3
• In chronic kidney disease patients, guidelines specifically recommend maintaining TSAT ≥ 20% 2, 1

Clinical Significance Based on Patient Population

For General Population:

• TSAT of 23% indicates adequate iron availability for red blood cell production
• No iron supplementation would typically be required at this level 3

For Chronic Kidney Disease Patients:

• TSAT of 23% meets the minimum threshold recommended by multiple guidelines:
  • The National Kidney Foundation KDOQI guidelines recommend maintaining TSAT ≥ 20% 2
  • The Canadian Society of Nephrology guidelines recommend TSAT ≥ 20% 2
  • KDIGO guidelines consider TSAT > 20% as adequate for most CKD patients 2

Relationship with Ferritin

The interpretation of TSAT should always be considered alongside serum ferritin:

• Even with a TSAT of 23%, iron supplementation might be considered if:
  • Ferritin is low (< 100 ng/mL in non-dialysis patients)
  • Patient is symptomatic for anemia
  • Patient requires high doses of erythropoiesis-stimulating agents (ESAs) 2

Special Considerations

Functional Iron Deficiency

• Some patients may have functional iron deficiency despite TSAT > 20%, particularly those on ESA therapy or with inflammatory conditions 2
• Studies have shown that some CKD patients with TSAT between 20-30% may still benefit from iron supplementation 2, 1
• The KDOQI guidelines note that studies showing benefits of IV iron included patients with baseline TSAT values between 23% and 31% 2

Inflammation

• In inflammatory states, TSAT may be falsely low despite adequate iron stores
• Conversely, ferritin may be falsely elevated as an acute phase reactant 1, 4
• This creates diagnostic challenges when TSAT and ferritin provide discordant information 5

Clinical Decision Making

For a patient with TSAT of 23%:

1. If asymptomatic with normal hemoglobin: No intervention needed
2. If anemic or symptomatic:
   • Check ferritin level:
     • If ferritin < 100 ng/mL: Consider iron supplementation
     • If ferritin 100-500 ng/mL: Consider iron if other causes of anemia excluded
     • If ferritin > 500 ng/mL: Generally avoid iron supplementation unless TSAT < 20% 2, 1
3. If on ESA therapy:
   • Higher TSAT targets (25-30%) may be beneficial to optimize ESA response 1

Conclusion

A TSAT of 23% is generally adequate for most patients, exceeding the minimum threshold of 20% recommended by major guidelines. However, clinical context matters, particularly in patients with chronic kidney disease, inflammatory conditions, or those receiving ESA therapy, where higher targets may be beneficial.