Direct Bilirubin (Conjugated) Lab Values

Hey there. My name is Abby. I’m here with nursing.com to go over a lab value with you. We’ll talk about conjugated or direct bilirubin. We’ll talk about its normal value, how it’s made in the body, and what might cause it to be increased or decreased. Let’s dive in.

A direct or conjugated bilirubin test measures the amount of direct or conjugated bilirubin in the blood. Now, let’s talk about direct versus indirect, or conjugated versus unconjugated for just a second. Bilirubin is a substance that your body makes when red blood cells break down. That’s a normal process. Bilirubin is also a part of bile that your liver makes to help you digest food. So, a small amount of bilirubin in the blood is normal. And, that is because some bilirubin is actually bound to albumin and that is unconjugated or indirect. So, indirect or unconjugated is going to be bound to albumin. Whereas, bilirubin that travels in through the liver is actually changed into conjugated or direct. It becomes a form that the body can actually excrete. And so a very small amount of that should actually pass into the urine and into the small bowel, and it’s actually what contributes to the color of urine and stool. 

Some clinical indications for when this would be drawn are if a newborn presents with jaundice. So, this is a picture of a neonate in the lights to help with the conjugation of the bilirubin. It also is, of course, used to investigate jaundice in adults to, uh, measure if there could be any type of duct block, whether that be in the gallbladder or in the liver. It helps to detect liver disease. If the liver isn’t functioning properly, it’s not going to be conjugating the bilirubin. It also helps to monitor the progression of hepatitis as previously mentioned. It can also tell us if there’s an issue with red blood cell breakdown and can even be indicative of a drug toxicity. 

Normal levels are between zero and 0.2 milligrams per deciliter. That’s a really, really tiny amount, right? And it’s taken in a plasma separator tube, like the green one you see on the slide. Lab values when they’re increased, of course, are going to indicate poor liver function or hepatitis. Certain medications can also disrupt the conjugation of bilirubin and hemolytic anemia, of course, because red blood cells, as they break down, create the bilirubin, and so this will cause, when those red blood cells are hemolyzed more bilirubin to be present in the bloodstream. Pregnancy, sepsis, these are all things that cause the bilirubin to be increased. And then, even exercise and alcohol abuse, these are all conditions that are actually really hard on the body, no matter how good they might be. And then, TPN the total parenteral nutrition that patients receive via IV can also create higher levels of bilirubin. 

Studies have been inconclusive about whether or not there’s a risk or an association with any disease process when the bilirubin level is decreased, so, maybe some good news. 

Some linchpins for this lesson are that the direct bilirubin is also known as the conjugated bilirubin, so this is the bilirubin that has gone through the liver and is able to be then excreted into the urine and stool. It evaluates for liver disease and certain hemolytic anemia. As well as here’s our normal value, Zero to 0.2. When it’s increased, liver disease or hemolytic anemia. When it’s decreased, or not sure if that’s a good thing or not, but it hasn’t been associated with any disease process yet.

Now, you all did great on this lesson and this wraps it up for our direct or conjugated bilirubin. We love you guys now, go out, be your best self today, and as always, happy nursing.

References:

• https://medlineplus.gov/ency/article/003479.htm
• https://www.uptodate.com/contents/diagnostic-approach-to-the-adult-with-jaundice-or-asymptomatic-hyperbilirubinemia?search=direct%20bilirubin&sectionRank=1&usage_type=default&anchor=H58687823&source=machineLearning&selectedTitle=2~150&display_rank=2#H58687823
• https://ltd.aruplab.com/Tests/Pub/0020033
• https://www.mayoclinic.org/tests-procedures/bilirubin/about/pac-20393041#:~:text=A%20common%20use%20of%20this,hepatitis%2C%20or%20monitor%20its%20progression.
• https://my.clevelandclinic.org/health/diagnostics/17845-bilirubin