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Order in Which You Draw Your Labs
Before we get started on talking about which order you draw your labs in, it’s important to understand why we do it. The first thing is that you have to realize that every blood tube is used for a different test. And the other important thing is they have different preservatives in them. These preservatives all do different things, like keeping the blood from clotting. The problem with this is that sometimes the preservative that’s in one tube can adversely affect the results of another test it’s in a different tube, so if you draw a blood sample and stick the syringe in one tube, pull it out, and put it into another tube, you could technically transfer that preservative from the first tube into the second, and it could change the outcome of the results.
I’ll give you an example. The lavender top tube, which is commonly used for your complete blood counts, has something called EDTA in it. The EDTA has a lot of calcium, and what could happen is if you put the syringe in that tube first and the calcium contaminates the needle and then you place it into the tube that you were sending out for your calcium levels, your calcium levels could actually report to be really high when they actually aren’t. So this is just an example in this is why we do that.
If you’re unsure of what the order is, or the specifics of a test, contact a lab in your facility and they will give you all the ins and outs of what specific tube types you’re going to need. Now let’s take a quick look at the different types of tubes that you may run into.
Now like we just talked about, you’re going to have different tubes for different tests. And a lot of these tubes are going to have different colors on the top and what that means is that they actually have a different preservatives and additives inside each of the tubes. Now we’re just going to hit some of the most common types of tubes and I’m sure that you’re going to run into some that you’ll see once and then never see again, but these are the most common types that you’re going to see it.
The first one is blood cultures and these are little jars. It’s really important with these that they are the first one drawn and will go into that in a few minutes but the thing that you need to understand is there specifics to how you draw them and how you put them in the tubes. There’s a great demonstration of this in one of our skills videos so go check that out.
Now the light blue tubes are the ones that you’re going to use for your coagulation studies. Your red and green tubes are the ones that you’re going to use for your chemistries, so like your basic metabolic panel, but the difference between the two is that the green has a heparin preservative in it to keep the blood from clotting. Typically you’re going to use your green tubes for fast results, and your red tubes are going to be sent for either more complex chemistries or even some certain serologies.
Like we talked about the last slide the lavender top tube has EDTA in it which is an anti-clotting preservative. It keeps the blood from clotting so that you can send out for things like CBC he’s or your hemoglobin or hematocrit. And the last one that were you’ll see is the gray tube which is really commonly used for things like either a glucose or a lactate. One thing that I do want you to remember from this is that this is not a comprehensive list. This is the list of the probably the most common types of blood tubes that you’re going to see, but there are going to be more in the hospital setting and in your facility so make sure that you ask questions, and talk to your a lab as you need to.
So what is the actual order that you draw them in? Well here you go.
First up is blood cultures, and you always want to make sure you do those first. Then do the light blue tubes, so things like your coags, then any chemistries which will either go in a red top tube or a green top tube, depending on what you need, then your lavender top tube for your CBC, and then if you have something like a lactate or a glucose, that’ll go in your gray tube last.
So what do you do if you only have a BMP and CBC? So they’re basically looking for chemistries and a complete blood count. Will do this, just remove all these other ones that you don’t need, so you’ll do a red or green top first, depending on what your facility says, and then we’ll do your lavender top tube.
Or what about a CBC on lactate? Well first you’ll do your lavender top tube, and then you’ll do your gray top tube.
Remember, we’re wanting to not contaminate tubes with additives or preservatives from other tubes. And there’s also one really other important point that I want to reiterate here. And that’s it if you are unsure of which tube to put it in, if there’s a possibility of a sample could get contaminated, or if it’s a really expensive test and you want to make sure that you do it right, then consider drawing a separate sample for that test. Just make sure that you’re using good nursing judgement, and that you’re not going to cause any unnecessary risk to your patient by drawing another sample. If everything is good, then get another sample and make sure that test is right, and send it out.
For today’s lesson we’ve really focused on are nursing concepts of lab values and also how we get those values by using our nursing skills.
So let’s recap:
Remember that all the tubes have specific additives to help make sure that blood is optimal for testing, so you want to make sure that you don’t contaminate other tubes by doing them in the right order.
If you have a question about a specific to protest, don’t hesitate to call up your lab and find out what the specifics are, and if you can even draw them with other tests.
Always start with your blood cultures, then do light blue, red or green, lavender, and then finally with gray.
And finally, If you ever are in doubt, you can always draw the separate sample for that test.
That’s it for today’s lesson on drawing labs. Make sure you check out all the resources attached to this lesson. Now, go out and be your best selves today.
❤️ Happy Nursing!
-Jon Haws, RN