Which statement correctly describes capillary samples for CBC testing?

• A. Capillary samples are generally used for CBC because they're quick.
• B. Capillary samples yield exact CBC results.
• C. Capillary samples contaminate results.
• D. Capillary samples are generally not used for CBC due to tissue fluid contamination and uneven distribution of cells.

Answer: (D)

Capillary blood is not ideal for a CBC because the sample can be contaminated with tissue fluid and the cells are not evenly distributed in such a small, capillary collection. A CBC needs accurate counts of red cells, white cells, and platelets, which are most reliable from venous blood drawn into an EDTA tube. Fingerstick samples can have variable fluid content, potential dilution or concentration shifts, and issues like squeezing or microclotting, all of which distort cell counts. So capillary sampling is generally not used for CBC due to tissue fluid contamination and uneven distribution of cells.