How do you prepare a blood sample for a microscope?
A thick smear being prepared. Preparing Blood SmearsIf you are using venous blood, blood smears should be prepared as soon as possible after collection (delay can result in changes in parasite morphology and staining characteristics). Thick smearsThick smears consist of a thick layer of dehemoglobinized (lysed) red blood cells (RBCs). The blood elements (including parasites, if any) are more concentrated (app. 30×) than in an equal area of a thin smear. Thus, thick smears allow a more efficient detection of parasites (increased sensitivity). However, they do not permit an optimal review of parasite morphology. For example, they are often not adequate for species identification of malaria parasites: if the thick smear is positive for malaria parasites, the thin smear should be used for species identification. Prepare at least 2 smears per patient!
Scratch Method for Thick smearsThe scratch method is an alternate method for making thick films that allows for improved adherence and faster turnaround times. The process is similar to making a normal thick film, but instead of using a stick to spread the blood, the edge of a glass microscope slide is used, while applying firm pressure to create small scratches in the underlying slide. The scratches allow for improved adherence of the blood film to the slide without affecting the smear morphology. The smear can then be stained as soon as it is dry, generally within 20-30 minutes of smear preparation. Reference: Norgan AP, Arguello HE, Sloan LM, Fernholz EC, Pritt BS. Malaria Journal 2013; 12: 231. Thin smearsThin smears consist of blood spread in a layer such that the thickness decreases progressively toward the feathered edge. In the feathered edge, the cells should be in a monolayer, not touching one another. Prepare at least 2 smears per patient! A thin smear being prepared.
Note: Under field conditions, where slides are scarce, national malaria programs (and CDC staff) prepare both a thick and a thin smear on the same slide. This works adequately if one makes sure that of the two smears, only the thin smear is fixed. Special Procedures for Detecting MicrofilariaeBlood microfilariae:
For additional information on making blood smears, call the Division of Parasitic Diseases at (404) 718-4110. Reference:Eberhard ML, Lammie PJ. Laboratory diagnosis of filariasis. Clin Lab Med 1991;11:4. What is the procedure involved in preparing blood cells for viewing under a microscope?Place a drop of blood onto a microscope slide. Add a drop of stain to the blood to make the cells easier to see. Carefully place a coverslip over the drop of blood. Sliding it slightly along the microscope slide will spread out the blood cells making them easier to see.
What should your blood look like under a microscope?Red blood cells are shaped kind of like donuts that didn't quite get their hole formed. They're biconcave discs, a shape that allows them to squeeze through small capillaries. This also provides a high surface area to volume ratio, allowing gases to diffuse effectively in and out of them.
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