Canadian Society for Medical Laboratory Science (CSMLS) Practice Exam

Using fresh EDTA blood is the best choice for the preparation of a blood smear for red blood cell (RBC) morphology. EDTA (ethylene diamine tetraacetic acid) is an anticoagulant that effectively prevents clotting by binding calcium ions in the blood. This is crucial for maintaining the integrity of the blood sample and ensuring that the cells remain in their natural, unaltered state. This allows for accurate visualization of the cells under a microscope, preserving their morphology and enabling effective analysis.

In contrast, other anticoagulants like oxalate, citrate, or heparin may introduce various complexities or artifacts that can affect the appearance of the RBCs. For example, oxalates lead to alterations in cellular morphology due to their effects on cell shape and structure. Citrated blood, while suitable for coagulation tests, is not ideal for morphology due to its anticoagulant properties that can cause changes in cell shape. Heparinized blood can also affect the morphology of white blood cells and platelets, making it less reliable for detailed RBC morphological assessments. Consequently, fresh EDTA blood stands out as the most appropriate choice for obtaining a clear picture of RBC morphology.