Diagnosis of the Fatty Liver Disease

Liver biopsy. This is the diagnostic test par excellence. This shows the presence of fat (steatosis), the inflammation associated with it and fibrosis (scar tissue). Since it is an invasive test, different non-invasive diagnostic tools have appeared in recent years to detect the presence of fat and fibrosis.

Serological biomarkers. These are substances in the blood that indicate the presence of fat or fibrosis in the liver which, taken together, help in the diagnosis of the disease. The indicators are calculated from analytical parameters and data in the patient's medical history. The most common are FLI to evaluate steatosis and FIB-4 to evaluate fibrosis.  

• The FLI is calculated from the levels of gamma-glutamyl transpeptidase (GGT) and triglycerides, the abdominal perimeter and body mass index (BMI). Steatosis is diagnosed with a FLI > 60 and discarded if < 30.  

• The FIB-4 is calculated from age, platelet count and transaminase (AST and ALT) levels. A FIB-4 < 1.3 in individuals under 65 years, or < 2 in those over 65, rules out fibrosis. However, values > 2.67 do suggest fibrosis, although this has to be confirmed by other diagnostic techniques.   

Abdominal ultrasound. This is a non-invasive radiological tool to check for steatosis and signs of advanced liver disease, such as cirrhosis. However, it is not reliable for establishing the amount of fibrosis. If the amount of fat is low, the ultrasound shows the liver as apparently normal. 

CT and MRI. These radiological tests are more sensitive than ultrasound and can detect the presence of steatosis and cirrhosis but are not used in daily clinical practice due to their cost, radiation and low availability.

Transition elastography. This technique is capable of detecting and quantifying fibrosis and steatosis quickly and at low cost. It is a non-invasive technique, using ultrasound. Elastography measures: 

• Liver stiffness in kilopascals (kPa), which correlates with the degree of fibrosis. Values ​​< 8 kPa are highly reliable for a lack of fibrosis, while values > 8 kPa indicate it may be present and must be investigated.  

• Newer elastography devices can also measure the CAP (Controlled Attenuation Parameter) which quantifies the degree of steatosis in dB/m. A CAP > 275 dB/m indicates an increased likelihood of liver steatosis. However, some factors, such as a lack of fasting or heart problems, may affect values; so it is always recommended to check and interpret the result with medical staff.