A blood smear is often used as a follow-up test to abnormal results on a complete blood count (CBC) to evaluate the different types of blood cells. The test lends information on the number and shape of these cells, which further help doctors diagnose medical conditions based on the blood conditions like malaria. Thick and thin blood smears help doctors know the quantitative percentage of red blood cells that are infected (parasite density) and what type of parasites are present. Thick blood smears are most useful for detecting the presence of parasites, because they examine a larger sample of blood Thin blood smears help doctors discover what species of malaria is causing the infection
Prior to the test it is important to inform your doctor about any prescription or over-the-counter medications, supplements, and vitamins you are currently taking. Certain medications can affect your test results. These include NSAIDs, antibiotics, and glucocorticosteroids. You should also tell your doctor about any existing medical conditions, such as hemophilia. Certain medical disorders, regular blood product transfusions, and the presence of certain types blood cancer will produce abnormalities on the blood smear result. It is important to discuss these matters with your doctor prior to the blood smear to avoid any possible diagnostic error.
Till date, microscopic examination of thick and thin blood smears are the easiest and most reliable test for malaria because blood smear test helps the doctors identify the malaria infecting species of Plasmodium. Other than malaria the blood smear test can be used to identify diseases like anaemia, myeloproliferative neoplasms, bone marrow disorders, and leukaemia
Blood smears are taken most often from a finger prick. A phlebotomist, a person specifically trained to draw blood, first cleans and sterilizes the injection site with an antiseptic. After withdrawing the blood, they cover the puncture wound with a bandage, after which you are free to leave. After this, the following steps are performed in a pathology: Place a drop of blood in the centre of a clean glass slide 1 to 2 cm from one end Place another slide(spreader)with smooth edge at an angle of 30⁰-45⁰ near the drop of blood Move the spreader backwards so that it makes contact with the drop of blood. Then move the spreader forward rapidly over the slide. A thin peripheral blood film is thus prepared. Dry it and stain it.