The page below is a sample from the LabCE course Bone Marrow Aspiration: Normal Hematopoiesis and Basic Interpretive Procedures. Access the complete course and earn ASCLS P.A.C.E.-approved continuing education credits by subscribing online.

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Coverslip Smear Preparation Technique

Coverslip smears are made on 22 x 22 mm coverslips using a technique similar to the pull prep method. If done correctly, both coverslips will have quality smears that will appear similar to a thumb print.

To create a coverslip smear preparation, a coverslip is picked up by the corner and the point is held between the thumb and forefinger in one hand. The other hand uses a capillary pipette to transfer a small drop of concentrated bone marrow on to the center of the coverslip. The capillary pipette is put down and a second coverslip is placed over the first to form a star shape. When the marrow has spread almost to the edges, the coverslips are slid apart using the protruding corners/points of the star. The motion is a parallel slide with no pushing or rotation of the wrist as the coverslips are slid apart.

Making smears on coverslips requires manual dexterity. Not only does the laboratory professional need to be proficient in the use of capillary tubes to pipette bone marrow, he/she must also be able to manipulate fragile coverslips without breakage. Staining also requires modified/adapted methods.

A 22x22 mm coverslip can be glued to a standard slide after staining to provide easy evaluation. Since only a minimal amount of bone marrow is needed, many smears can be made from a small bone marrow sample. Another advantage is the small amount of storage space required. Three dozen coverslips will easily fit in an envelope and would take considerably less storage space compared to the same number of regular slides.