What is fatty liver disease (hepatic steatosis)?
Hepatic steatosis, sometimes called "fatty liver disease", is an excessive buildup of fat in liver cells. It is now strongly associated with metabolic syndrome: overweight or obesity, type 2 diabetes, high blood pressure and abnormal blood lipids are very often found together in affected people. Editorially, steatosis is more of a marker and consequence of this metabolic syndrome than an independent, causal cardiovascular risk factor the way smoking or diabetes are.
Why it is often silent
Hepatic steatosis usually causes no symptoms at an early stage. It is most often discovered incidentally, during a routine blood test showing slightly elevated liver enzymes (AST, ALT), or an abdominal ultrasound done for another reason. It is precisely because it is silent that a simple screening tool like the FIB-4 is useful: identifying early on who would benefit from further testing.
What is fibrosis, and why early detection matters
Over time, the inflammation associated with fat buildup can lead to fibrosis: a progressive buildup of scar tissue in the liver. At an advanced stage, fibrosis can progress to cirrhosis and its complications. The FIB-4 score, used in the tool above, is an initial screening test for this advanced fibrosis: a low result has a strong negative predictive value (it reliably rules out advanced fibrosis), while a high or indeterminate result warrants further testing (Fibroscan, Fibrotest, or another specialized test) with a doctor.
The limits of this score
The FIB-4 is meant for initial screening, not for monitoring a liver disease that has already been diagnosed and is being managed: if a diagnosis has already been made by a doctor, this test provides no additional information, hence the filtering question asked before starting. Its reliability is also lower under age 35 and past age 65; beyond that upper threshold, age becomes a major confounding factor in the calculation — which is why the low threshold is raised starting at age 65 to partly compensate for this bias.
