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Diagnostic Testing
Biochemical Testing
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Biochemical testing for iron status is
recommended for patients with
- Symptoms or signs suggestive of hemochromatosis:
- Severe weakness or fatigue.
- Unexplained joint or abdominal pain.
- Signs of liver disease, diabetes, or heart problems.
- Impotence, infertility, and loss of menstrual periods.
- Porphyria, hepatitis, or other liver diseases.
- Abnormal blood tests consistent with hemochromatosis:
- elevated transferrin saturation,
- elevated serum ferritin,
- elevated transaminase (indicative of liver disease), or
- elevated blood glucose (indicative of diabetes).
Evaluation for other causes of these medical problems should also be
performed.
Biochemical testing for iron status is also recommended for family members of diagnosed hemochromatosis patients.
- These individuals have an increased risk of developing iron overload
and are an ideal group for targeted prevention efforts.
The
simplest tests that indirectly indicate iron overloading are serum iron and
iron-binding capacity, which allows calculation of percent transferrin saturation.
Serum ferritin correlates well with iron stores but its normal value rises
with age and varies with gender; it can also be elevated with liver disease,
inflammation, and neoplasm.
Biochemical tests include
- Serum iron (SI).
- Total iron-binding capacity (TIBC).
- Unsaturated iron-binding capacity (UIBC).
- Transferrin saturation (TS).*
- Serum ferritin (SF).
*TS is sometimes called iron saturation because the majority of
laboratories use a surrogate TS marker instead of measuring transferrin
levels. These surrogate measures are serum iron and iron-binding capacity
(total iron-binding capacity [TIBC] or unbound iron-binding capacity [UIBC]).
Measuring transferrin for TS requires immunologic measurement, a procedure
that is costly and too time-consuming for most clinical laboratories.
Recommended laboratory tests for the workup of a patient you suspect may
have hemochromatosis are
- Fasting transferrin saturation test (TS)
- SI and either TIBC or UIBC are usually used to calculate TS.
- TS = (SI / TIBC) X 100
- TS = (SI / (SI + UIBC)) X 100
- Serum ferritin test (SF)
Note: Due to patient compliance issues, a TS value obtained from a nonfasting
blood draw can be used to screen a patient for iron overload. Non-fasting TS
values greater than 60% indicate iron overload. Non-fasting TS values
between 45% and 60% are considered evidence of borderline elevation. A
repeat TS from a fasting blood draw should then be obtained.
How do I order a transferrin saturation test?
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