The ALD/NAFLD index answers one narrow question — in a liver already known to be fatty or inflamed, is alcohol or metabolic disease the more likely cause — and it needs a laboratory blood draw: AST and ALT from a liver panel, MCV from a complete blood count, plus your height, weight and sex. It does not tell you whether you have liver disease; it assumes that is already settled, by raised enzymes, an ultrasound showing fat, or a biopsy, and only sorts the cause.
The index came out of the Mayo Clinic in 2006, built in patients with biopsy-proven steatohepatitis, because drinking histories are often incomplete and the two diseases look almost identical under the microscope. Both tests are routine and cheap, but this is a lab measurement, not a home one.
What you need
- AST (aspartate aminotransferase) and ALT (alanine aminotransferase), from a standard liver panel.
- MCV, the mean corpuscular volume, which comes on any complete blood count.
- Your height and weight, to give body mass index.
- Your sex, because the model weights men and women differently.
- A reason to be asking — established or strongly suspected fatty liver. This is a tiebreaker between two causes, not a screening test.
Nothing else is used: no GGT, no imaging, no fibrosis panel. If you do not know your body mass index, the Body Mass Index (BMI) gives you that input first.
How the measurement works
Alcohol and metabolic overload damage the liver in similar ways but leave different traces in routine blood work. Alcohol injures mitochondria, which are rich in AST, and depletes the vitamin B6 that ALT production needs, so AST tends to run higher than ALT — classically more than twice as high. In metabolic fatty liver that is usually reversed, with ALT the higher of the two, until advanced fibrosis flips it. Heavy drinking also enlarges red blood cells, so a high MCV is an old and fairly specific alcohol signal, while a high body mass index is the signature of the metabolic cause and pulls the other way.
The four values are combined into one signed number with published weights. Each pushes in a known direction: a higher AST-to-ALT ratio and a higher MCV move the score toward alcohol, a higher body mass index moves it toward the metabolic cause, and being male shifts it toward alcohol. Rather than doing that by hand, enter your values into the ALD/NAFLD Index (ANI).
How to read the result
The output is a single number that can be positive or negative, and the sign carries the answer. Above zero the profile favors alcohol-related liver disease; below zero it favors the non-alcoholic, metabolic form. There is a single cut point, so no band table.
The magnitude adds confidence, not severity. A score far from zero means the blood pattern is lopsided and the classification is fairly secure; a score near zero is an unresolved question rather than a weak answer. Read it next to your drinking history and your metabolic risk factors.
What it does not tell you
It does not say how damaged the liver is. Cause and stage are separate questions; scarring is estimated with a fibrosis score such as the FIB-4 Fibrosis Index, or with elastography. It also forces a binary the real world does not respect: many people drink heavily and carry metabolic disease at once, a combination now recognized in its own right in fatty liver nomenclature. And it excludes nothing else — viral hepatitis B and C, autoimmune hepatitis, hemochromatosis, Wilson disease and drug-induced liver injury are ruled out separately.
Each input can be wrong for reasons unrelated to the liver. MCV rises with vitamin B12 or folate deficiency, hypothyroidism and several medications, and falls with iron deficiency or thalassemia, which can hide an alcohol effect entirely. AST rises after muscle injury, hard exercise or hemolysis, and the AST-to-ALT ratio climbs in any cause once cirrhosis develops.
It is weakest in two places: advanced, decompensated disease, where the model was reported to lose accuracy, and the general population, where most people have neither diagnosis and any such score loses predictive value. It also does not define a safe amount to drink. The index exists because drinking histories are underreported, not because it beats an honest one.
Related reading
- Steatohepatosis
- MCV
- Which Blood Tests Reflect Aging and How to Read Them
- How to Improve Metabolic Health: A Practical Guide
Disclaimer. This article is for information only and does not replace medical advice. Talk to a qualified clinician before changing anything about your health.