What does a transferrin (Total Iron-Binding Capacity) level of 188 and a Total Iron-Binding Capacity (TIBC) of 229 indicate?

Interpretation of Transferrin 188 and TIBC 229

A transferrin level of 188 with a TIBC of 229 indicates iron deficiency, as the transferrin saturation (TSAT) calculated from these values is approximately 82%, which is above the normal range of 20-50% and suggests iron overload. 1

Calculation and Understanding the Values

• Transferrin saturation (TSAT) is calculated using the formula: TSAT (%) = (serum iron / TIBC) × 100 1
• Transferrin can be converted to TIBC using the formula: TIBC (μmol/L) = Transferrin (g/L) × 25.1 1
• Normal TSAT range in adults is typically 20-50%, with values >50% potentially indicating iron overload 1

Clinical Significance of These Values

• The high TSAT of 82% suggests possible iron overload conditions rather than iron deficiency 1
• TSAT reflects iron that is readily available for erythropoiesis, while serum ferritin reflects storage iron 2
• When TSAT is high (>50%), this indicates that a large proportion of transferrin binding sites are occupied by iron, suggesting excess iron 1

Differential Diagnosis to Consider

• Hemochromatosis or other iron overload disorders 1
• Acute or chronic liver disease, which can affect transferrin production 3
• Recent iron supplementation or transfusion, which can temporarily elevate TSAT 1
• Laboratory error or sample collection issues, as diurnal variation can affect iron levels 1

Additional Testing Recommended

• Serum ferritin measurement is essential to confirm iron overload, as it is the most specific test for iron status 2, 4
• Serum transferrin receptor (sTfR) testing may help distinguish between iron overload and other conditions 3
• Complete blood count to assess for anemia or other hematologic abnormalities 5
• Liver function tests to evaluate for liver disease that might affect transferrin production 3

Important Caveats

• Several factors can affect TSAT measurement, including:
  • Diurnal variation (TSAT levels rise in morning and fall at night) 1
  • Recent meals (serum iron concentration increases after eating) 1
  • Inflammation and infection (can decrease serum iron concentration) 1
  • Recent IV iron administration (should not evaluate iron parameters within 4 weeks of infusion) 1
• Day-to-day variation within individuals is greater for TSAT than for hemoglobin concentration 4, 1

Follow-up Recommendations

• If iron overload is confirmed with additional testing, genetic testing for hereditary hemochromatosis should be considered 1
• Evaluate for symptoms of iron overload including fatigue, joint pain, abdominal pain, and skin pigmentation 1
• If the patient has been receiving iron supplementation, this should be discontinued pending further evaluation 1
• Repeat testing may be warranted to confirm results, particularly if the values are unexpected based on clinical presentation 4