Current time:0:00Total duration:10:42
0 energy points

Introduction to lab values and normal ranges

Video transcript
So I have a slip of paper. Let's go through these lab values. I actually put down a number of values down that we're going to pretend for a moment are my labs. And you can see the range, and the units next to them. So let's go through it piece by piece. And actually, while I do it, I'm actually going to show you some shorthand techniques, so that you can understand, if you ever see this in the future, what it refers to. So this is some shorthand that people have come up with. This isn't necessarily something I've come up with. I learned it from folks ahead of me. But it's been used not just in the US, but most parts of the world. It's pretty uniform. So if you're looking at these labs, here's a quick way to transcribe them. So imagine that you have to quickly put it on a piece of paper and move on. This is how you would do it. So you would draw a little stick diagram like that. And in the far left, you'd put the number 5. And this refers to the first row, the White Blood Cell row. And we know that the value is 5,000, so that's what the 5 represents. And it's understood that that number is in thousands of cells per milliliter. So if you see a 5, you know we're talking about thousands of cells per milliliter. And the next question is, well, what are those types of cells, if you actually were to look at them? We know they're white blood cells. But exactly what type they are is actually in the six rows beneath. So these six rows tell you the breakdown of this number. So that's why they're percents. And so the 5,000 cells break down into segmented neutrophils. I'm going to write that as an S with a 61. And bands, there are 3% bands. Lymphocytes are 29%. And then we have monocytes at 4%, basophils at 1%, and eosinophils at 2%. So these percentages for the different types of white blood cells are going to add up to 100, right? So let's just double-check. We've got 7 and 29 is 36, and 3 is 39. Yep, 100%. So that's how you quickly can see the different types of white blood cells that are floating around in your body. That's what those numbers represent. So then the next two numbers, hemoglobin and hematocrit, go in the top and bottom of this stick diagram. And again, whenever you see these numbers like this, I could look at that and immediately figure out that that's the red blood cell content. Those two numbers both reflect red blood cell content in the blood. And then the last cell on this side represents the platelet count. And 227 represents 227,000 cells per microliter. So before, we were talking about milliliters for the white blood cells. But now, for the platelets, we're talking about microliters. And in fact, I'll put "cells" in quotes, because we know it's not really cells. These are little cell fragments that are the platelets. So that 227,000 tells you about how many platelet cell fragments are floating around in one microliter of blood. So that's the first chunk of data. So that's all this information, summarized very quickly in that stick diagram. Now let's move on to the chemistries. And so if someone orders a Chem 7, then that would be the first seven of these. And if they order a Chem 10, then that would be all 10 of these. So this is how you would draw this out as a stick diagram. It kind of goes like this. And the Chem 10, the last three, go in here. So the sodium goes in the top left. And below that is the 4.3 for potassium. And just going systematically all the way through it, so for chloride, it's 103. Bicarbonate goes as 22 right below that. And then the creatinine goes in this cell, 0.8. And then the blood urea nitrogen-- sometimes they call that the B-U-N, that's just the first letter of these three-- is 15. And then the fasting glucose is 92. And then the calcium goes in the top of this little wishbone-shaped stick diagram. That goes right there. The magnesium goes on this side. And the phosphate goes on this side. So that's the Chem 7 on top. And the Chem 10 would be all of that together. And then, at the bottom, we have some liver enzymes. And also, there's a stick diagram for that, as well, kind of a fast way to draw it. And it's basically just an x. So the top of the x is two numbers. So you usually write the total bilirubin like this, 1.1. And then you put a slash. And then you put the other number there, the direct bilirubin, 0.1. And then on the left, you put the AST. And on the right, you put the ALT. And at the bottom, you put the alkaline phosphatase, 76. So this is how the numbers break down. And so, again, if you ever see any of these stick diagrams and you're wondering what they refer to, now you have broken the code. You know what number goes where. So if you see, for example, this number at 22, you immediately know that they're talking about the ALT. So this is the way that people quickly diagram things. And now I know, when people look at labs, the first thing they want to know is, hey, is this good or bad? And so, they want to look at these values, and they want to compare them to the ranges. They want to say, hey, does this fit into the normal range that people expect? So let's talk about that. Let's talk about normal range and what normal means exactly, because I know that's the first thing most people will want to look at. So let me draw out what a normal curve would look like. So if you actually, let's say, took everybody, let's say 10,000-- it's not everybody, but let's say a big chunk of people-- 10,000 people and asked them all to tell you their white blood cell count. They will give you, of course, many different numbers. Probably wondering what you're doing with that information. But let's say they give you their answer. And let's say you plot it all on a curve, and you draw a little diagram. This would be basically what you would find. You'd say, OK, most people have a white blood cell-- and this is white blood cell count. Actually, sorry. This is white blood cell count down here. And this is, of course, in thousands. We said thousands per milliliter, thousands of cells per milliliter. And this is frequency. This is the number of people. I'll just write f for frequency. So you would say, OK, while there are a lot of people in this range right here-- and in fact, 95% of people fall in to this middle section in this area. So this is definitely the bulk of people that fit between 4.5 and 10. And that's actually how most of these ranges are decided upon. They say, OK, where do the bulk of folks lie? And it's usually between those numbers that are in the range. And that also means, if you think about it, that there is, of course, somebody out here and somebody up here, right? I mean, that is, by definition, going to happen. You're going to have 5% of people in one of those two tails combined. So whenever you see a range, just keep in mind that there is some normal variance, they're called, that kind of go above or below that range. But that range usually captures the majority of folks. So when thinking about that, when thinking about what exactly goes into a normal range, consider some of the things that could make what is normal differ. So for example, let's say I check someone's hematocrit. Let's say I'm looking at the hematocrit, and I want to find out if it's normal or not. If I look at a baby's hematocrit, but I use, let's say, an adult range, then it would be very, very unusually high. So a newborn baby has a very high hematocrit, so I really should be comparing it to other newborn babies. So age is really important to consider. So you want to make sure that the range of values is age-appropriate. You also need to make sure that gender is considered. So for example, the normal range for men's hematocrit is a little bit higher than the normal range for women's hematocrit. So range matters for age and also for gender. Now, different labs will also differ. So it's actually quite interesting. You can even go online and see what the normal range is for a lot of these things I have here. And the numbers will be a little bit different from what I've shown you. So if you go from one lab to another, you'll get different numbers. And in fact, lab technique also matters. So even within a lab, depending on the technique that they use to get an answer to something, the range could differ. And that actually matters, particularly for things like this. So these IUs that I put down here, they stand for units, or international units. And that's specific to a certain type of lab assay that's done. And again, that depends on the exact assay that's done. And that's going to change the range of values that you get there. So consider the technique. And finally, consider this situation. So if you have, let's say, a person who is supposed to come in for a fasting glucose. And usually, you're told, just don't eat anything overnight. And don't have breakfast. And come in and get your blood taken first thing in the morning. That's a pretty common scenario. Then you would have a normal fasting glucose. And it should be below 100. But let's say, by accident, you decide to have a little snack in the morning, because that's your usual thing. You have some toast. Your blood glucose could go up as a result. So that glucose result could be OK, if someone knows that you didn't fast, really. You had a little snack. So that situation changed. So your metabolism is going to make that range go up. So only for fasting glucose is the number below 100 normal. Otherwise, it could be higher. Now consider a situation where you're taking a medication. Let's say you're on a medication that causes your potassium to go down. So you're on a drug. It causes potassium to leave your kidneys and go into the urine. Your potassium value would then go down. I would expect it to be lower, right? Because you're taking your medication. And so some of these ranges are going to change, depending on what medications you take, what you had for breakfast that day, or not had for breakfast, what kind of medical conditions you have. So it's going to definitely depend on the situation. So whenever you look at ranges and values, and you want to see if you are in the normal range, just consider all these things that could explain why your number may or may not be within that range.