A peripheral blood smear (PBS) test is a technique healthcare providers use to examine your red and white blood cells and your platelets under a microscope. Your healthcare provider may order a peripheral blood smear along with a complete blood count (CBC).
A peripheral blood smear test is a technique healthcare providers use to examine your red and white blood cells and your platelets. Unlike some blood tests that are analyzed by a machine, healthcare providers do the analysis by looking at blood cells under a microscope.
Your healthcare provider may order a peripheral blood smear along with a complete blood count (CBC), or if you already had CBC and it shows abnormal blood cell activity, they might order a PBS. For example, your CBC results may indicate your white blood cells, red blood cells and/or platelets appear abnormal or that you have an abnormal number of any given type of cell. A microscopic view of your cells may help your healthcare provider find out how and/or why your blood cells look abnormal or you have an abnormal number of cells.
Results from a peripheral blood smear test aren’t a diagnosis. Healthcare providers make diagnoses based on your medical history, physical examination and results from laboratory tests, like a PBS.
Cleveland Clinic is a non-profit academic medical center. Advertising on our site helps support our mission. We do not endorse non-Cleveland Clinic products or services. Policy
Here are other reasons why your healthcare provider might order a peripheral blood smear test:
To understand what PBS tests show, it may help to have more information about the role your blood cells and platelets play:
A peripheral blood smear test shows how your blood cells and platelets look under a microscope. Looking through a microscope, your healthcare provider may see:
Healthcare providers use peripheral blood smear tests to diagnose blood disorders, blood cancers and infections. These conditions can happen when bone marrow cells mutate and become abnormal cancerous cells known as blasts. Examples include:
Healthcare providers do this test by spreading a drop of your blood onto a glass plate, turning the drop into a thin film. They treat the blood with chemicals that highlight blood cells’ specific characteristics. Then, they examine the sample under a microscope.
Healthcare providers order peripheral blood smear tests for specific reasons. You may have had a CBC that showed an abnormal result, and your healthcare provider is doing a peripheral blood smear test to learn more. You may have certain symptoms, and a peripheral blood smear test will help your healthcare provider diagnose the cause. Regardless, they’ll explain why they recommend a peripheral blood smear test and what the results mean.
A note from Cleveland Clinic
A peripheral blood smear test is a technique healthcare providers use to examine your red and white blood cells and your platelets. This test gives them a clear picture of changes in your blood cells and platelets that may be a sign of disease. A peripheral blood smear test is an important part of diagnosing disease. It is, however, only one part of the process. Your healthcare provider may be able to diagnose your disease when they combine test results with what they learned during a physical examination and your medical history. They may order additional tests before making a diagnosis. But they know you’ll have questions about the process and test results. If you have concerns about this test or any other test, ask your healthcare provider for more information. They will be glad to answer your questions.
Last reviewed by a Cleveland Clinic medical professional on 04/15/2022.
Learn more about our editorial process.