What is the importance of preparing a good blood smear?
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Peripheral blood smear, blood smear analysis, peripheral blood film, smear, manual differential, manual DIFF Show
What is this test?A blood smear is a type of blood test. It looks at the appearance, number, and shape of your red and white blood cells and platelets to see whether they are normal. A blood smear can also detect parasites in your blood. It is now more common to have blood analyzed by a computer. But blood smears may still be routinely done to look for certain diseases. A blood smear is checked by a lab scientist (pathologist) or healthcare provider who specializes in blood or infectious diseases. These specialists look at the blood cells on a slide. Sometimes a blood smear shows information that's not found by a computer. Why do I need this test?You may need this test if you have any of the problems below:
Healthcare providers often use a blood smear to confirm the diagnosis for certain diseases. For example, if a child has bouts of severe, unexplained chest pain, the child might have sickle cell anemia. This is an inherited disease that can be identified through a blood smear. You may also have this test to check your blood cell count if you have had chemotherapy. This test may help your healthcare provider see if the treatment is working. What other tests might I have along with this test?You may also have a complete blood count. This test looks at the size and number of platelets and red and white blood cells. Another test often done with a blood smear is a reticulocyte count. This is done by staining and counting the number of premature red blood cells. These are red blood cells that have left your bone marrow early. You may also have a chemistry panel, or a blood chemistry test. This test measures substances, such as electrolytes, sugar, and protein, in your blood. You may also have a bone marrow biopsy. This is a test that looks at the blood cells inside your bone marrow. Bone marrow is a spongy substance inside some large bones. Bone marrow makes blood cells. For this test, the healthcare provider collects a tiny amount of bone marrow with a needle. What do my test results mean?Test results may vary depending on your age, gender, health history, and other things. Your test results may be different depending on the lab used. They may not mean you have a problem. Ask your healthcare provider what your test results mean for you. The results of a blood smear might include the number, size, and shape of your red blood cells. The results also might tell your healthcare provider the number and type of your white blood cells, the number of platelets, or even if you have a parasite. Your test results will be either normal or abnormal. Your healthcare provider will interpret that result based on your symptoms, the diagnosis your provider suspects, or the treatment you are having. A blood smear can be used to help diagnose or check on many conditions, such as:
The accuracy of the results depends on the skill and experience of the person looking at your blood smear. Talk with your healthcare provider about the results. How is this test done?The test is done with a blood sample. A needle is used to draw blood from a vein in your arm or hand. Does this test pose any risks?Having a blood test with a needle carries some risks. These include bleeding, infection, bruising, and feeling lightheaded. When the needle pricks your arm or hand, you may feel a slight sting or pain. Afterward, the site may be sore. What might affect my test results?Ask your healthcare provider if you can eat or drink before the test. How do I get ready for this test?You don't need to prepare for this test. But be sure your healthcare provider knows about all the medicines, herbs, vitamins, and supplements you are taking. This includes medicines that don't need a prescription and any illegal drugs you may use. Slide one? Tossed. Slide two? Tossed. Slide three? No good either. Ten slides later and you still don’t have a fantastic, easy to read slide. Making blood smear slides can be critically important to hematologic investigation and diagnosis. They can be a useful tool to assess everything from white blood cell disorders, such as leukemias, to various types of acquired or congenital anemias, to broader organ issues like liver or kidney disease. However, the effectiveness and accuracy of that interpretation depend on the quality of the slide. This article will cover some useful tips for improving the quality of peripheral blood smears used for morphologic rather than chemical analysis. The Ideal Blood SmearOne of the most common types of peripheral blood slides is the wedge slide. An ideal slide is neither too thin nor too thick. It should end about two-thirds to three-fourths of the way down the slide. The end of the smear should be thin enough that it has a rainbow-like reflectiveness about it, and there should be no streaks at the very edge. Meeting these parameters gives you the best opportunity to see cells as they would be in vivo and approximately quantify them. Slide Making BasicsWhen making a wedge smear, there are two slides involved: the pusher slide and the patient slide. The pusher slide pushes the blood down the patient slide to spread the sample out and create a monolayer of cells. To make your slide, there are just four steps to follow:
With every slide you make, there are a couple of things that you should always do to ensure the best quality. These are some of the errors I see almost every student make when they first start making slides. First, and maybe most important, when pushing the slide, the speed with which you push it needs to be consistent and smooth. Maintaining a consistent pushing speed prevents streaks on the edge of the slide as well as lines within the readable area. Simply trusting in yourself can help improve your slide-making skills. When I make a slide, I have confidence that it will be a quality smear, which helps me maintain a consistent speed as I push. Second, let the blood spread all the way out before you start to push. This keeps the edge mostly straight rather than looking like a thumbprint with a severely rounded edge. Holding the SlidesThere are many ways to hold the slides, depending on what works best for you. Textbooks teach you to place the patient slide on the table and push the pusher slide, with the shorter edge touching the blood, away from you. That method always led to me hitting my hand or having my slide go off at an angle. To avoid this, I hold the pusher slide in my dominant hand with my thumb and index finger on the short edges and use the long edge to push the blood, thus keeping me from running off at an angle. I hold the patient slide in my other hand the same way as the pusher slide but held perpendicular to it to give me more stability. In the end, all that matters is that the pusher slide edge is flat against the patient slide. Try different ways of holding the slides to see which feels best for you. Further Changes You Can MakeOnce you know how you want to hold the slides, there are a few adjustments you can make as you push the slide, depending on the quality of blood:
In my experience, the main parameter that affects how the blood pushes is the hematocrit level. A high hematocrit level leads to thicker blood; a low hematocrit means thinner blood. The thickness of the blood affects how quickly it spreads against the pusher slide and how far down the slide it pushes. You can control for this variation by adjusting the items listed above. When I make a slide, I know what adjustments to make as soon as I see the blood spread against the pusher slide. Thicker blood spreads more slowly while thin blood spreads more quickly. I made a chart to highlight the changes you can make. ParameterHigh hematocrit (thicker)Low hematocrit (thinner)Pusher slide speedSlowerFasterAmount of bloodMoreLessPusher slide angleDecrease (<30°)Increase (>30°)Knowing the patient’s age and health status can help you determine the best way to make your slide. Working with Blood with High Hematocrit LevelsHigh hematocrits occur most frequently in newborns and patients with certain cancers such as polycythemia vera. You must push more slowly to ensure that the blood spreads far enough down the slide. Using a larger drop size can help get enough blood to spread the desired two-thirds to three-fourths of the length of the slide. You can also change the angle of the pusher slide. Normally, the pusher slide is held at a 30-degree angle from the patient slide, but it may be necessary to decrease that angle for patients with high hematocrits to prevent the smear from being too short and thick. Working with Blood with Low Hematocrit LevelsThinner blood behaves exactly the opposite as blood from patients with high hematocrit levels. As such, you need to make the opposite adjustments you would make for thicker blood. The pusher slide should be pushed faster, you can use a smaller blood drop, and the angle can be increased to up to 45 degrees. As with everything, practice makes perfect. Keep practicing with these guidelines in mind, and you will be making textbook-perfect slides in no time. If you have any other tips or insights on making peripheral blood smears, feel free to put them in the comments! Why is it important to have a good blood smear?The test provides information on the number and shape of these cells, which can help doctors diagnose certain blood disorders or other medical conditions. Irregularities in the number or shape of your red blood cells can affect how oxygen travels in your blood.
What is the most important thing to remember when creating a blood smear?The Ideal Blood Smear
An ideal slide is neither too thin nor too thick. It should end about two-thirds to three-fourths of the way down the slide. The end of the smear should be thin enough that it has a rainbow-like reflectiveness about it, and there should be no streaks at the very edge.
What is the importance of a well made well stained and carefully examined peripheral blood film in performing WBC differential count?A well-made, well-stained, and carefully examined peripheral blood film can provide valuable information regarding a patient's health. More can be learned from this test than from many other routinely performed hematologic tests.
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