Full Blood Count Quiz

See Section. Option A is correct. A film that is one cell thick allows individual red cells to be examined without their outlines being hidden by overlapping cells. The examiner can then assess size, shape and staining, including the pale centre of a normal red cell. If the layer is too thick, overlap can make normal cells appear abnormal or conceal a genuine abnormality. A thin film therefore improves morphological assessment, meaning examination of how the cells look. Spreading, drying, fixation and staining are separate preparation steps, each contributing to a useful final slide.

Concentrating white cells (B) is not the purpose of the monolayer: spreading separates cells rather than packing them together. Clotting (C) would trap and distort cells, making the specimen less useful. Methanol fixation (D) preserves an already prepared film; it does not explain why individual cell outlines must be visible. Stains colour normal as well as abnormal cells (E), according to their components rather than selectively recognising disease.