Chronic iron accumulation in diseases such as haemochromatosis or thalassaemia can be confirmed by direct measurement of iron in a liver biopsy or by carrying out a Desferal (desferrioxamine) test. This involves giving the patient an intramuscular injection of the chelating agent, Desferal, and collecting the urine excreted over the following six hours. Iron is normally excreted via the faecal route and urinary iron concentrations are low (about 0.5 µmol/L): following Desferal injection, urine iron normally increases by up to 18 µmol/L, whereas in patients with a storage abnormality, urine iron increases to over 50 µmol/L.
The Hepatic Iron Index (liver iron concentration in µmol/g divided by the patient’s age in years) was proposed by Bassett et al. to differentiate genetic haemochromatosis from alcoholic siderosis, both of which result in increased liver iron concentrations. This index exceeds 1.9 in haemochromatosis but not in heterozygotes or alcoholic liver disease. The index has been evaluated in several centres and shown to be a useful diagnostic tool.
Sample Requirements and Reference Ranges for Iron
| Sample Type | Urine, liver |
|---|---|
| Container | Universal container |
| Precautions | A needle biopsy should be about 1 cm in length and should be put directly onto the wall of a Universal container without lint. No preservative should be added. If there is any delay before sending, store frozen.
Please mix 24 hour urine well before taking an aliquot. |
| Minimum volume* | Urine: 1 mL of a 24 h collection; liver: 1 to 5 mg |
| Reference ranges | |
| - urine | < 1 µmol/L |
| - desferrioxime test | < 18 µmol/vol (normal following Desferal injection) > 45 µmol/vol (indicates an iron-storage abnormality) < 1.0 µmol/24 h (normal in absence of injection) |
| Turnaround time | 1 week |
| Method | Inductively Coupled Plasma Mass Spectrometry |
* This is the absolute minimum volume; these volumes are insufficient to carry out a repeat analysis in the event of an analytical problem.