Tau protein

Other names: Desialated Transferrin; Beta 2 Transferrin

Tau protein is beta 2 transferrin, a protein that is found in cerebral spinal fluid; it is not usually found in the blood or other bodily fluids, including fluid from the nasal passages. Cerebral spinal fluid (CSF) is usually only found in the brain and the spinal canal; however, an injury to the head or back, which causes the membranes that cover the brain and the spine to tear, may cause cerebral spinal fluid to leak out. Fluid may start to drip from the ears (known as otorrhoea) or the nose (rhinorrhoea).

When is the test used?

The test is used to determine whether or not cerebral spinal fluid has leaked out following an injury; the test is used to analyse a sample of watery fluid, which may or may not be cerebral spinal fluid.

The test is ordered when watery fluid is leaking from the ear or nose and doctors suspect that it may be cerebral spinal fluid; the test detects tau protein, which is present in CSF but not in other bodily fluids. The test is usually carried out on patients who have had accidents or suffered injuries which have affected their head or spinal column.

How is the test carried out?

The test involves a blood test, as well as a collection of the suspicious fluid, which doctors suspect might be cerebral spinal fluid. The blood test will be done by collecting and analysing a sample of the patient’s blood; a needle is inserted into the vein and the blood is drawn out and collected in a syringe. The sample is then placed in a bottle, labelled with the patient’s name and sent off the laboratory for analysis.

What do the test results show?

If the test results show that tau protein is present in the sample of fluid, this usually indicates that the fluid is cerebral spinal fluid; however, in some rare cases, tau protein may be found in other fluids and further tests may be required. Tau protein may be found in the blood when a patient has a genetic variation, which causes them to produce certain types of transferrin; it may also be found in the blood if the patient has consumed a large amount of alcohol. The blood sample will always be analysed at the same time as the fluid sample.

Leakage from the ears or nose is very rare; in most cases, this leakage is due to infection and the test will only be ordered if a doctor is suspicious about the cause of the leakage.

Specific Blood Tests

Blood Test Guide

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