A brush biopsy is a very non-invasive method to collect cells from an individual for testing purposes. A brush with a mildly abrasive tip is moved over the top layer of the skin, and cells loosely on the surface are picked up and collected by the tip. A genetic brush biopsy relies on this cell sample from the patient to provide material for genetic testing. In the case of the test for nasopharyngeal cancer, the cells are analyzed for the presence of genetic material from the Epstein-Barr virus. This test is therefore very accurate and at the same time very tolerable for the patient.