Doctors use blood tests, imaging tests, and sometimes liver biopsy to diagnose NAFLD and NASH.
Blood test: You have NAFLD or NASH if your blood test shows increased levels of the liver enzymes alanine aminotransferase (ALT) and aspartate aminotransferase (AST). Your doctor may perform additional blood tests to find out if you have other health conditions that may increase your liver enzyme levels.
Your doctor may use the following imaging tests to help diagnose NAFLD:
Ultrasound: Ultrasound uses a device called a transducer, which bounces safe, painless sound waves off your organs to create an image of their structure.
Computerized tomography (CT) scans: CT scans use a combination of x-rays and computer technology to create images of your liver. For a CT scan, a health care professional may give you a solution to drink and an injection of a special dye, called contrast medium. Contrast medium makes the structures inside your body easier to see during the procedure. You’ll lie on a table that slides into a tunnel-shaped device that takes the x-rays.
Magnetic resonance imaging (MRI): MRI machines use radio waves and magnets to produce detailed images of your organs and soft tissues without using x-rays. Imaging tests can show fat in your liver. These tests can’t show inflammation or fibrosis, so your doctor can’t use these tests to find out whether you have simple fatty liver or NASH. If you have cirrhosis, imaging tests may show nodules, or lumps, on your liver.
Fibroscan (Elastography): Fibroscan (Elastography) is also called liver stiffness measurement, uses either ultrasound or MRI to measure the stiffness of the liver. Scar tissue increases the stiffness of the liver. Elastography can show how much scarring is present with some reliability.
Liver biopsy: During a liver biopsy, a doctor will take a piece of tissue from your liver. A pathologist will examine the tissue under a microscope to look for signs of damage or disease. A liver biopsy is the only way to detect liver inflammation and damage to diagnose NASH. Doctors don’t recommend this test for everyone with NAFLD. Your doctor may recommend a liver biopsy if you are more likely to have NASH or if your other tests show signs of advanced liver disease or cirrhosis.