Iron deficiency anemia and anemia of chronic disease
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Iron deficency anemia diagnosis
- So the first step to making a diagnosis of iron deficiency anemia is taking a look at the patient. Seeing what signs and symptoms they're complaining of. So iron has a couple of different roles in the body. So let's talk about some of the roles of iron in the body. So firstly, there's one role that we already talked a little bit about, and that is that iron is responsible for making hemoglobin. So it makes hemoglobin. And because of that, when a person is deficient in iron, they have troubles making hemoglobin, and that leads to anemia. And so the patient will present with signs and symptoms typical of anemia, such as fatigue, weakness, looking pale, feeling short of breath, right? Now iron serves lots of different roles in the body because it serves as a cofactor for lots of different proteins and enzymes in the body. So the other role of iron I'm gonna very descriptively write down is other, OK? Because it serves too many roles to list out individually. So for example, iron is really important for the health of skin, hair and nails. So when a person becomes deficient in iron, they can have this thing called koilonychia, which refers to spoon-shaped nails, and I can't draw it out. But if you were to look up the picture, you'd see that quite literally the nails are in the shape of a spoon. Also people who have iron deficiency can experience pica, which is a desire to eat inedible things, such as dirt or ice. And iron deficiency can also lead to restless leg syndrome. And we don't know exactly know exactly how iron deficiency leads to restless leg syndrome, but we do know that there's a very strong association between the two. And again, this is all because iron serves as a cofactor for lots and lots and lots of different enzymes throughout the body. So somebody who is deficient in iron presents not only with anemia, but also with all of these other symptoms. So the first step, if a patient comes in and has signs and symptoms of anemia, and maybe a couple of these other symptoms, maybe you'd start to think that perhaps there's an underlying iron deficiency anemia. So the first thing you would do is draw some blood and check how many red blood cells they have. And if they do have a true decrease in the number of red blood cells, then you'd say that definitively they do have anemia. But that tells you nothing about the cause of the iron deficiency anemia. So to establish iron deficiency as a cause of anemia, you'd have to do something called iron studies. But if we can ever hope to understand anything at all about iron studies, first we have to learn a little bit about the physiology of iron in the body. So here is a diagram, and the reason why I put this in here is to show that when we consume iron through the diet, it goes in through the esophagus, through the stomach, and then it stops right here, the first portion of the small intestine called the duodenum. The duodenum. And the iron is absorbed at the duodenum. So expanding that a little bit, here are the cells that line the duodenum, and when iron presents in front of there, it gets absorbed through these cells and into the bloodstream. But the iron doesn't float around in the bloodstream, willy nilly on its own. Instead, it's bound to this protein called transferrin. So transferrin transports the iron through the bloodstream. And it transports it through the bloodstream, and it takes it to distant sites where it's needed. But most of the iron is actually transported to the liver because the major site of iron storage in the body is the liver. The iron is brought into the liver, and it's stored in these cells called macrophages. So here the iron is being brought into the macrophage, and again, the iron isn't just left alone and unbound in the macrophages. Instead it's bound to this really large protein called ferritin. And you might be asking yourself, well, why is the iron, whether it's in the bloodstream or whether it's inside a cell, why is it always being chaperoned by a protein? Why is it never left on its own? And the answer to that, the very important answer to that, is that when iron is left alone, when it's not bound to anything, it'll float around and it will steal single electrons from different molecules, and it'll generate something called free radicals. And free radicals are really damaging to cells and molecules. So that's why whenever you find iron in the blood, or whether you find it in the cells, it's always bound to something. In the blood it's bound to this chaperone protein called transferrin, and inside the cells when it's being stored, it's bound to a chaperone protein called ferritin. So the storage form of iron is called ferritin. OK, so now we know enough to talk about iron studies. So if you suspect that somebody has iron deficiency anemia, you go ahead and order iron studies. And these are some of the values that would come back. So let's talk about what we'd see in a patient who's iron deficient. So if the patient is iron deficient, you'd expect their serum iron to be low, right? That's not too hard to understand. What about their percent saturation? This refers to how many of the sites on transferrin are occupied by iron. So if we're in a state where we're deficient in ron, you'd expect that a lot of the sites on transferrin are empty, they're unoccupied by iron. And so the percent saturation would be low. And it's a good fact to know that the normal percent saturation in a person who isn't iron deficient is 33 percent. So 33 percent of the binding sites on transferrin are usually occupied by iron. Let's look over the total iron binding capacity for a second and talk about the ferritin. So in a person who's iron deficient, you'd expect that their ferritin, or the amount of storage iron they have, is decreased, right? Maybe not initially so. Maybe when you initially become iron deficient you start using up some of your storage iron. But eventually, after a prolonged period of iron deficiency, your storage iron, your ferritin, would also decrease. Now let's talk a little bit about the total iron binding capacity. This value actually reflects the amount of transferrin. Amount of transferrin. And that makes sense because as your transferrin goes up, the amount, the binding capacity you have for iron goes up. And as the amount of transferrin you have goes down, the binding capacity of iron goes down. So our body does this really cool thing where it recognizes that it is deficient in iron. And it tries to compensate for that by making more transferrin so that the transferrin can go out into the bloodstream and suck up more of this iron. So as a compensatory mechanism in iron deficiency, your transferrin levels, and hence your total iron binding capacity actually increases, OK? This is really important. This is our body's main mechanism for combating the iron deficiency. So if these iron studies came back with these values, you could definitively say that your patient has iron deficiency anemia. But that tells you nothing about why they're iron deficient. So the last step would be to determine why the patient is iron deficient. So let's slide over and take a look at this. You may remember we created this chart to sort of highlight the main causes of iron deficiency anemia. So as your last step, you'd take a look at the patient's age and their gender and see what could the possible cause of iron deficiency be. If you have a woman who's pregnant, well you could speculate it's probably because of the increased demand that she's iron deficient. If you have a woman who experiences heavy menstrual flow, then menorrhagia would be the reason, and perhaps explore that further. You could do an ultrasound of the uterus, of the pelvis to see maybe if there are fibroids present that are accounting for the increased menstrual flow. In a young man, or even in a young woman, who's experiencing signs of gastric reflux, you might say, well perhaps peptic ulcer disease is present, and you could do an endoscopy, which is inserting a camera through the mouth to take a look at the esophagus and the stomach for the presence of ulcers to account for the iron deficiency. And in elderly people, very, very importantly, you always have to consider colon cancer or colon polyps as the cause of iron deficiency anemia. So if an elderly individual walks in with new onset iron deficiency anemia, you should always do a hemoccult test, a hemoccult test. And what that looks for is blood in stool. So it tests the stool for the presence of blood. And if that's positive, if you find blood in the stool, then you can do a colonoscopy, which is inserting a camera through the colon to look for a possible cancer of a polyp. So these are some of the common causes of iron deficiency anemia, and these are the three steps that we just went through, are the three steps you'd go through to diagnose someone with iron deficiency anemia.