From the Guidelines
To order a Transferrin Saturation (TSAT) test, you should request both serum iron and total iron binding capacity (TIBC) measurements, as TSAT is calculated as (serum iron ÷ TIBC) × 100%. The test requires a morning fasting blood sample to avoid diurnal variations in iron levels 1. When interpreting results, normal TSAT ranges from 20-50% in adults. Values below 20% suggest iron deficiency, which may indicate conditions like iron deficiency anemia, chronic blood loss, or malabsorption. Values above 50% suggest iron overload, potentially indicating hemochromatosis, hemosiderosis, or excessive iron supplementation.
Key Considerations
- TSAT should be interpreted alongside other iron studies including ferritin, which reflects iron stores 1.
- Inflammation can affect results, as ferritin increases during inflammatory states while TSAT may decrease, so consider C-reactive protein levels when interpreting borderline results.
- Repeat testing may be necessary to confirm abnormal values, particularly in patients with concurrent acute illness that might temporarily alter iron parameters.
Interpreting Results
- A TSAT of < 20% in hemodialysis patients has been considered to be indicative of iron deficiency, but this is not an accurate discriminator between patients who are or are not iron deficient 1.
- In the presence of inflammation, the lower limit of serum ferritin consistent with normal iron stores is 100 mcg/L, and hypoferraemia should be considered likely if TSAT is < 16% and serum ferritin is between 30 and 100 g/L 1.
Clinical Application
- The evaluation of anaemia in any given patient is always incomplete if the inflammatory status is not clearly defined 1.
- Transferrin saturation levels > 800 g/L are considered toxic and should be avoided 1.
From the Research
Ordering a TSAT Test
To order a Transferrin Saturation (TSAT) test, you will typically need to:
- Consult with a healthcare provider to determine if the test is necessary for your specific situation
- Provide a blood sample, which will be sent to a laboratory for analysis
- The laboratory will then measure the levels of serum iron and total iron-binding capacity (TIBC) in your blood, and calculate the TSAT value
Interpreting TSAT Test Results
The TSAT test results can be interpreted as follows:
- A low TSAT value (typically less than 20%) indicates iron deficiency 2
- A normal TSAT value does not necessarily rule out iron deficiency, as inflammation and malnutrition can affect TIBC levels 2
- Serum iron and TIBC tests may not provide additional information in the diagnosis of iron deficiency anemia if serum ferritin is available 3
Considerations for TSAT Test Results
When interpreting TSAT test results, consider the following: