ALT, AST, Bilirubin direct/indirect, protein, albumin, alkaline phosphates, etc.
Please help me understand what the blood levels mean and how they are interpreted. How can the doctor determine if it’s alcohol related? Medication induced? Gall bladder related? Something else?
Here’s a scenario to add context: Patient suddenly has very high ALT (175) & AST (75) but all other values are in the normal range, including other non-LFT blood panels. What would this typically indicate and what would be the next course of action?
In: Biology
I am a clinical biochemistry technician. This could get long, but I’ll try to ELI5.
We call them Liver Function Tests, but really, they’re mostly just liver enzyme tests. The only part of an LFT that’s truly measuring function would be the bili and the proteins.
**ALT and AST** – These are two enzymes found in the liver, as well as other tissues like muscle, heart, kidneys, etc. They are not supposed to be in your blood at high levels. If they are, that means some physical damage to any of those tissues has occurred. They are not very specific to the liver or any particular form of liver disease.
AST also has a special application – the AST/Platelet ratio. This is used as an easy way to estimate the severity of cirrhosis; liver scarring. A damaged liver makes AST levels high. The liver makes Platelets, so a damaged liver makes fewer platelets. High AST/Low Platelets = a High AST/Platelet ratio, which suggests the cirrhosis is very bad.
**Alkaline Phosphatase** – This is another enzyme. What we measure in your blood comes mostly from your liver and your bones, but its also in the placenta, intestine, and kidney. The liver ALP comes specifically from the canal that bile flows through toward your gallbladder. So, it is more specific for when you have a biliary disease.
Like with ALT and AST, when theres physical damage to those cells (e.g. because of a gallstone), it spills out into your blood. Because it comes from bones too, high ALP can alternatively indicate you’ve got an issue with your bones, not your liver.
**GGT -** Like the other enzymes, GGT is also found everywhere in your body (except muscle), but it’s *mostly* in the liver. It’s raised in most forms of liver disease but unlike ALP, it doesn’t go up if you have bone issues. Thus, Raised ALP without a raised GGT can suggest a bone problem rather than a liver one. GGT is also known to be particularly high when the damage to the liver is caused by alcohol.
**Bilirubin and Direct Bilirubin -** Bilirubin is made when red blood cells die. The liver modifies bilirubin so it can be excreted into your bile. Total bilirubin measures all the bili, modified and unmodified. Direct bilirubin measures only the modified bilirubin. Total – direct = the amount of unmodified bilirubin.
Having lots of bilirubin suggests somethings happening that has you either make lots of bilirubin (you’ve lots of dying RBCs) or somethings stopping it being sent away into your bile (like a gallstone).
Having lots of bilirubin and lots of it is **unmodified** suggests that what’s happening is you’re having lots of red blood cells break down suddenly and its exceeding your livers capacity to process. It’s likely you have a haemolytic disease.
**Protein and Albumin -** The liver is the main site of protein synthesis in the body. Albumin should make up about 55-65% of all the protein in your blood. There can be lots of reasons why your albumin may decrease, but one of them is very severe chronic liver disease; there’s just not enough liver left to make the amount of albumin you need. Someone with chronic liver disease may have low protein and albumin and raised liver enzymes, whereas someone with a more acute illness will just have the raised enzymes.
So back to the question – An apparently healthy person who suddenly has isolated ALT and AST has *probably* simply just done some intense exercise and caused those enzymes to leak out from their muscles into their blood. I would ask them to rest and retest in a week or so.
You need to speak to your doctor. Do not ask strangers online for medical advice. Your doctor and only your doctor can interpret your medical test results for you.
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