Alright! In this video, I am going to go over some diagnostic tests that are associated with the immune system. If you're following on cards, I am on card number 10. We're first going to talk about white blood cells. So your white blood cell count should be between 5,000 and 10,000. That's what the normal range is. If your patient has a white blood cell count over 10,000, that is considered leukocytosis, and that is a strong indicator that the patient is fighting some sort of infection. If the patient has a white blood cell count under 4,000, then that is considered leukopenia. And if a patient has leukopenia, that could be due to a number of causes which include cancer, an autoimmune disorder, or certain medications or infections can cause a drop in the number of white blood cells. But if your patient has leukopenia, then they are at high risk for infection because they have insufficient white blood cells to help fight off those infections. Alright. Let's talk about neutrophils. Neutrophil count should be between 2,500 and 8,000. If we have neutrophils under 2,000, that is considered neutropenia. We may also have something called banded neutrophils or a left shift. And that's an important thing to know what that means. So normally, the bone marrow is producing these neutrophils and releasing them out into the body to help fight infection. If the body is fighting an overwhelming infection, that bone marrow cannot keep pace, right? They are producing all the neutrophils they can, but it's not enough to fight this overwhelming infection. So they start releasing immature neutrophils out into the body. It would be like if we're fighting a war, if our country's fighting a war, and we've sent all our adult soldiers and they're still not getting the job done. It's a really bad war. We start sending our kids and our teenagers and 13-year-olds, immature soldiers out there to try to fight that war. It's kind of like the same thing that the bone marrow's doing. If the infection is so bad that the mature neutrophils that they've released into the body aren't getting the job done, they'll start sending out immature neutrophils before they are fully functional. So again, that is considered a "left shift" or banded neutrophils. Okay. Let's now talk about ESR. So ESR stands for erythrocyte sedimentation rate. And if a patient has elevated levels of ESR-- so normal levels will be under 20. If they have levels above 20, then that is a strong indicator of the presence of inflammation in the body. In addition, CRP, which is C-reactive protein that's another indicator of inflammation. So normal levels of CRP are below three. So if your patient has a value above three, then that is also an indicator that they have some kind of inflammation in the body. The way I remember CRP is it has three letters, right, CRP, and so that helps me to remember that normal levels are under three. Another test that your provider may order for your patient is something called a differential white blood cell count. So if the provider is trying to figure out what type of infection the patient may have, if they have cancer or some kind of autoimmune disorder, this test can be helpful. So there are five main types of white blood cells that are present, and this count will tell us how much is present of each kind. So with neutrophils, neutrophils make up the largest percentage of white blood cells in the body, typically between 55 and 75% of the white blood cells. We may have elevated levels of neutrophils when a patient is fighting an acute bacterial infection. So neutrophils are like the first responders of the white blood cells. They are the first to arrive on-site to help fight a virus or bacteria. So our little hint to remember that is that neutrophils are first to neutralize the threat. Okay, then we have lymphocytes. Lymphocytes make up between 20 and 40% of the white blood cells, and they may be increased when a patient has a bacterial infection, a viral infection. They can also be increased with leukemia and lymphoma as well. Then we have monocytes. So monocytes make up about 2 to 8% of the white blood cell count. They may be elevated with bacterial infections as well as tuberculosis. Then we have eosinophils, which make up just 1 to 4% of the white blood cells. They are elevated with allergic reactions as well as parasite infections. And then finally we have basophils. Basophils make up just 0.5 to 1% of the white blood cells. They are elevated during allergic reactions. So basophils will release histamine when you're having an allergic reaction, and with that histamine, you may need to take an antihistamine, such as Benadryl, to help cope with the symptoms of all that histamine. So the little saying we have here to help you remember that is that with basophils, you might need Benadryl, because those basophils release that histamine and Benadryl is an antihistamine to help you with those symptoms. And hopefully it will help you remember that with basophils, you're thinking allergic reaction. So that is it for the differential white blood cell count. When I come back for my next video, we will start getting into disorders, starting with Lupus. Thank you so much for watching.