These tests show us if anything is happening in the liver, though they do not tell us what the cause is. The following also appear on a general lab test Comprehensive Metabolic Panel (CMP):
** ALT and AST: Liver enzymes, also called transaminases; previous names were SGPT and SGOT. “Normal” is usually <40 or <60 IU/L, depending on the lab (although liver specialists say it should be <30 in men and <25 in women). The degree of elevation depends does not necessarily correlate with the seriousness of illness. For example:
- Acute Viral Hepatitis (A,B,C,D,E) can cause levels to rise >1,000. I had one patient with Hepatitis A whose ALT was >10,000, and he wasn’t very sick
- Acute liver failure from poisoned mushrooms, acetaminophen (Tylenol®) overdose, drug toxicity, and herbal preparations can cause extremely high elevations
- Severe damage from Alcoholic Hepatitis might be accompanied by only modest elevations like 200 – 300; the AST is usually higher than ALT
- Many drugs cause levels to double or triple, without anything bad happening. Statins are one example. We discontinue the medication if the ALT reaches 5-times its upper limit
- Various chronic Liver Diseases may only cause a doubling or tripling of the ALT, but result chronic liver failure (Cirrhosis) leading to eventual transplant or death
- To truly determine danger of liver failure, we need to order Prothrombin Time, drawn in a different test tube (see below)
** Alkaline Phosphatase: Elevated in liver disease, but especially in gallbladder disease, and other rare diseases of the liver and “biliary tract” (see Gastrointestinal System — Anatomy). Alkaline Phosphatase can also be elevated due to certain bone diseases (e.g. cancer), pregnancy, and even from having recently eaten.
** Bilirubin: High levels make us jaundiced (eyes & even skin turn yellow). Can be due to any liver disease; it’s very serious if due to the gallbladder. Other causes of high bilirubin include Pancreatic cancer, and Hemolysis (red blood cells break apart for various reasons, nothing to do with the liver). Some people have genetically high bilirubin, called Gilbert’s Syndrome (pronounced as in French), which is harmless.
** Albumin: A protein made by the liver. If someone with chronic liver disease develops a low albumin, they likely have liver failure (Cirrhosis) (see below).
** GGT: A transaminase like ALT & AST (above). It’s not included on the routine CMP. High levels don’t tell us much, since there are lots of false-positives. Normal levels reassure us there’s nothing happening in the liver.
“Synthetic Function” — When the above tests are elevated, they indicate something is happening in the liver, but don’t tell us how bad the damage is. For the latter, we test for what’s called “synthetic function.” One job of the liver is to synthesize proteins; if those proteins are normal, then the liver is doing all its work, detoxifying not only drugs but especially all unrecognized contaminants in the food we eat, before they circulate through the body.
The two proteins we use to measure Synthetic Function are:
- Albumin, noted above. This is especially relevant for chronic liver failure (cirrhosis).
- Prothrombin, the protein that helps blood to clot. It has to be drawn in its own special test tube, the test we order is “Prothrombin Time” (Protime, PT), reported in terms of an INR. Normal INR is 1.0. We worry if it’s 1.6 or above. The PT/INR is key to evaluating chronic cirrhosis, but especially for acute liver failure.
- The PT is also used to monitor anticoagulant treatment with warfarin; an appropriate INR is usually between 2.0 and 3.0. It’s OK for it to be high when we intentionally want to prevent clotting. It’s BAD for it to be high on its own, meaning the liver isn’t working.
Whenever we worry about the liver, we need to evaluate synthetic function. Oftentimes clinicians don’t remember this; they order the basic Comprehensive Metabolic Panel (CMP) which includes LFTs, but forget to order a Protime separately. If your provider ever tells you they’re concerned about liver disease, be sure they include the PT in their lab order.