Liver Function Tests

In this lesson we're going to talk about liver function tests.

When we do liver function tests, we look at multiple different values. The first three that we look at are liver enzymes specifically. Aspartate aminotransferase or AST, alanine aminotransferase or alt, and alkaline phosphatase or alp are going to be the three levels that we really look at and we're going to get into the ins-and-outs of those in a little bit. But here is a normal levels. AST is 12 to 37 units per liter, alt is 13 and 69 units per liter, and ALK PHOS is 40 to 130 units per liter.

We also include these other tests in a liver function test. We take a look at calcium which is 8.4 to 10.2 milligrams per deciliter, we look at total bilirubin which is 0.1 to 1.2 milligrams per deciliter, LFTs also look at proteins. Albumin is 3.5 to 6 grams per deciliter and total protein is six to eight grams per deciliter. We also look at glucose which is 70 to 115 milligrams per deciliter.

Now let's get to the nuts and bolts of liver function tests.

So I'm sure that you looking at these and wondering what the heck's going on. Well let's go through that. The column on the left are enzymes that are specific to liver function test that we're going to monitor. The column on the right are things that are affected by liver disease, it will go into that in a minute.

If we look at the values of AST, ALT and ALK PHOS, you can see here that they are all produced in more than one place other than the liver. What that means is that if you have elevations in any one of these enzymes, and not in the others, you should suspect that something else is going on beside the primary liver problem. Typically your AST and your ALT will go up together, and they're typically associated more with liver issues. The Alk Phos is produced both in the liver in the bone, but it's also indicative of congestion issues, so if you have liver congestion at the level of the gallbladder, then you can suspect that maybe you have some gallbladder or biliary issues going on with your patient. If you have overall liver failure, you're going to see all three of these levels go up. So the big takeaway here is that one single increase in one of these three values does not mean that it is a primary liver issue. You need to look at them in trends over time, you need to look your patient, and you need to look at them all together.

So let's take a quick look at these other values.

We take a look at calcium when we're looking at liver function tests because it's typically associated with the albumin. It's going to go where the albumin goes. And because albumin and other proteins are made in the liver, we also monitor those values. Also we take a look at total bilirubin, because that gives us an indication as to whether the liver is functioning so that it can break down the bilirubin and send it into the GI tract. The last one we looked at is glucose, and we want to make sure that we're not depleting our glycogen stores because of liver damage.

We have several different lessons on all of these particular Labs so I want you to go check those out so that you can understand more in detail. But for our purposes of the liver function test, this is how they play a role in this particular process.

For our liver function tests, we want to submit these labs in a green top tube, and we will also want to make sure that our patients are fasting so that your patients nutrition doesn't get in the way of the test result.

So what happens if all of these values are elevated? Well we have to look at the liver being the primary cause of the problem.

Some of the causes of these increases in liver function tests are different types of hepatitis, so we could be infectious or it could be viral. There are different types of cirrhosis that can contribute to decrease liver function which includes alcohol. There's also another liver disease called non-alcoholic fatty liver disease that will increase your liver function test. Also consider different types of toxicity that will affect your liver values. There's another condition called Wilson's disease which is copper storage disease, And that's where the liver can't eliminate copper out of the body. So you get this build up of copper, And that'll cause the increase in the liver values. This is a chronic disease, and but it's typically managed with medications to help patients cope with it.

Other causes for elevated liver function values are going to be gallbladder disease, so if there's inflammation of the gallbladder, inflammation of the bile duct, or gallstones, this will cause an increase in liver values. Also different types of cancer can cause elevated liver values.

Overall decreased liver values are not very common but when they are there usually attributed to malnutrition. So by improving your patients diet you can actually improve those liver function tests.

For this lesson, we're really focusing on the gastrointestinal and liver metabolism looking at these liver function tests, in addition to those lab values.

Okay so let's recap.

First, remember there lots of components to liver function tests.

Increases in single numbers do not particularly indicate liver disease, which is why you need to look at them together.

You want to submit them in a green top tube, and make sure your patient is fasting.

And last increase value of can indicate primary liver disease both chronic and acute. But take a look at all of your values together.

And that’s it for our lesson on liver function tests. Make sure you check out all the resources attached to this lesson. Now, go out and be your best selves today. And, as always, happy nursing!!