Testing and Diagnosis
Have seen a lot of questions around testing for Hemochromatosis, here is some guidance – thanks to The Hemochromatosis Society: http://hemochromatosis.org.uk If you think you might have Hemochromatosis make an appointment with your Doctor.
Diagnosis of Genetic Hemochromatosis (GH) is often made late. This is dangerous because untreated iron overload leads to organ damage and other problems, much of which is irreversible. Any of the common symptoms – especially in combination – should lead your doctor to arrange tests that may confirm GH at the earliest opportunity.
Diagnosis is made through any or a combination of the following tests. You may hear references to genotyping, or molecular diagnosis, which are terms referring to definitive genetic testing results, or phenotyping, which is a term used when referring to analysis of the physical symptoms or traits of a genetic condition.
Transferrin saturation (TS)
TS is the ratio of two simple blood tests, which indicates how full (saturated) the body’s system for transporting iron is. Serum iron is divided by total iron binding capacity (TIBC) to give TS as a percentage. Normal average is 30% (slightly higher in men than women) and if on two occasions TS is over 50% in men or 45% in women, iron overload is very likely and your doctor should then measure serum ferritin.
Serum ferritin (SF)
This is an indicator of the amount of iron stored in the body. Levels significantly over 300µg/l (micrograms per litre) in men and post menopausal women, and 200µg/l in women are further evidence of GH. It should be realised that in the early stages of iron accumulation, serum ferritin may be within the normal range and thus raised TS with a normal serum ferritin level does not rule out a diagnosis of GH.
A serum ferritin result on its own cannot be used to diagnose GH because other factors can influence SF levels, for example medication, inflammation, alcohol and other medical conditions.
A simple genetic test for the HFE gene mutation is positive in over 95% of those affected. It will also identify family members at risk of loading iron.
Testing is using a blood sample from which DNA is extracted and analysed.
Prior to genetic testing and on the delivery of results you may also be referred to a geneticist or genetic counsellor to discuss the implications for your family and the interpretation of results.
Liver function and liver iron tests
Your doctor will request a number of blood tests to check your liver, known as liver function tests. Liver problems can be an indicator of iron deposits building up.
A form of magnetic resonance imaging (MRI) scan called FerriScan or LiverMultiScan (these are brand names) is now increasingly in use as a way of directly measuring liver iron concentration.
MRI is usually preferred to biopsy as it is cheaper, non-invasive, quicker and more accurate. However in some cases a biopsy might still be necessary; a small sample of the liver is removed using a biopsy needle, which is checked to see whether tissue damage such as cirrhosis is present.
Liver tests are generally recommended if serum ferritin has been recorded above 1000µg/l, or if there is other evidence of abnormal liver function.
Liver transient elastography or Fibroscan (a brand name) is similar to an ultrasound scan and is widely used as a way of checking for fibrosis and more severe forms of liver damage such as cirrhosis.