Doctors may be required to investigate and rule out a range of other illnesses that share the same symptoms before haemochromatosis is suspected.
Abnormal iron levels are often the only sign of haemochromatosis. Therefore, the most important tests for detecting iron levels in the blood are the transferrin saturation and serum ferritin tests.
Transferrin saturation (TS)
Transferrin is a protein that binds iron in the blood serum and carries it around your body. This test measures the level of iron in your blood against the capacity of the blood iron binding protein (transferrin) to bind it. This is known as the Total Iron Binding Capacity or TIBC.
The transferrin saturation (TS) is the concentration of serum iron divided by the TIBC expressed as a percentage. A value over 55% in a man and over 50% in a woman may indicate an overload of iron. If this is the result you may be asked to provide another sample after an overnight fast so that a more accurate reading can be gained.
Serum ferritin (SF)
Ferritin is the protein that stores iron in the tissues. Small amounts of ferritin are found in the blood serum. As the amount of iron in your body increases, so do the levels of ferritin in the serum.
Ferritin is measured in micrograms (mcg) per litre. The upper limit is set at 300 for men and 200 for women. Levels over this limit are seen as an indication of haemochromatosis. Usually both transferrin saturation and ferritin are measured when testing for haemochromatosis. However, measurement of ferritin is not totally reliable as iron levels may increase when the liver is inflamed and can also increase in medical conditions other than haemochromatosis. Additionally, your ferritin levels may be within normal range during the early stages of haemochromatosis. The TS may be depressed in a patient who has inflammation (such as arthritis) or an infection.
Genetic test
Genetic testing is a recent development in haemochromatosis and is used to determine whether you have the HFE gene mutation. Doctors may use the test to identify the cause of high iron levels detected in the TS and SF tests.
Your blood cells will be examined for the HFE gene mutations C282Y and H63D by using a
simple blood test. In some cases this may be a finger prick test in which a small drop of blood is applied to a card and taken away for examination.
If homozygosity for C282Y or compound heterozygosity for C282Y/H63D is found, the test
is ‘positive’. Genetic testing is positive in over 90% of people with iron overload.
Liver function tests
If liver disease is suspected, liver function tests (LFTs) may also be used. These involve a number of separate examinations, each looking at different properties of your blood to gain an idea of how much your liver is inflamed or damaged in its ability to work properly.
In particular, doctors will be concerned to measure levels of the liver enzymes ALT and AST which are increased during liver inflammation (hepatitis).
Liver biopsy
The genetic test has reduced some of the need for liver biopsy to confirm haemochromatosis. However, if you have high serum ferritin (over 1000 mcg per litre) or any sign of liver disease, doctors may use a liver biopsy to confirm their diagnosis and to assess the severity of any liver damage caused by fibrosis/cirrhosis.
During a liver biopsy a tiny piece of the liver is taken for study. To do this, a fine hollow needle is passed through the skin into the liver and a small sample of tissue is withdrawn.
As well as measuring liver damage, liver biopsy enables chemical analysis of the iron concentration in the tissue sample. This is useful when iron overload is suspected in people who do not have the ironloading genotype (the abnormal gene pairs likely to cause haemochromatosis).
Other tests
In addition to blood tests and liver biopsy it may be necessary for medical staff to use ‘imaging’ equipment to help them detect the presence of iron build-up in your body. This is most likely to be a MRI scan, although ultrasound technology is sometimes used to guide a liver biopsy.
Magnetic Resonant Imagery (MRI) is a special tube scanner used to provide a detailed view of the liver. It creates powerful magnetic fields by releasing radio frequency energy to act on water molecules in your body. A type of radio signal is returned and picked up by the MRI equipment. This is relayed to a computer that can generate very detailed cross-sectioned images (or ‘slices’) of your liver area.
Diagnostic technology has been developed specifically for iron-overloading disease. ‘Ferriscan’ is a procedure that has been developed to analyze the MRI scans themselves in order to measure iron concentration.