What dilution is used for manual RBC count?

The appropriate dilution for a manual red blood cell (RBC) count typically involves a specific ratio of blood to diluent to ensure accurate counting under a hemacytometer. In this case, a 1:200 dilution of EDTA blood with saline is commonly used. This dilution allows for a sufficiently low concentration of RBCs in the sample, making it easier to visualize and count them without overcrowding the counting chamber.

The choice of using EDTA blood is crucial because EDTA acts as an anticoagulant, preventing the blood from clotting and preserving the integrity of the cells for accurate counting. Saline serves as the diluent, which helps maintain the appropriate osmotic environment for the cells.

The other options involve dilutions or combinations that may not provide the necessary conditions for a reliable manual RBC count. For example, a 1:50 or a 1:5 dilution may result in too high a concentration of RBCs, making it difficult to count accurately, while a 1:10 dilution of serum and hemolysate does not align with standard practices for a full blood sample, which is necessary for a comprehensive RBC count.