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This article forms part of our Tests and results' series for 2013, which aims to provide information about common tests that general practitioners order regularly. It considers areas such as indications, what to tell the patient, what the test can and cannot tell you and interpretation of results.
Keywords
elasticity measuring techniques; chronic liver disease; FibroScan
The use of non-invasive tests to stage the severity of liver disease (ie. scarring) is now well established in the management of patients with chronic liver disease. This is because assessment of liver scarring provides prognostic information and assists in establishing treatment priorities. One such technique, transient elastography (TE), is a simple, safe and efficient way to estimate liver scarring. FibroScan® (EchoSens, Paris) is the most popular non-invasive device used to assess liver 'hardness' (or stiffness) via TE in Australia. When performed in the appropriate clinical setting, TE provides a reliable method of detecting cirrhosis and excluding significant fibrosis, particularly when the results are supported by clinical and laboratory data.
What is FibroScan® and transient elastography?
FibroScan® is a non-invasive device that assesses the 'hardness' (or stiffness) of the liver via the technique of transient elastography. Liver hardness is evaluated by measuring the velocity of a vibration wave (also called a 'shear wave') generated on the skin. Shear wave velocity is determined by measuring the time the vibration wave takes to travel to a particular depth inside the liver.1 A graphical representation of this is provided on the screen (Figure 7). Because fibrous tissue is harder than normal liver, the degree of hepatic fibrosis can be inferred from the liver hardness. To improve test reliability a minimum of 10 valid readings, with at least a 60% success rate and an interquartile range of <30% of the median value, are taken with the results expressed in kilopascals (kPa).1·2
How is the test performed?
With the patient lying supine, an ultrasound-like probe is placed on the skin over the liver area, typically in the right mid-axillary line. The patient feels a gentle 'flick' each time a vibration wave is generated by the probe {Figure2). Typically the test takes around 10 minutes to perform and causes no patient discomfort. In general, patients should have fasted for at least 2 hours before...