In the TP measurement, how is plasma obtained from the hematocrit tube?

• A. Break the hematocrit tube just above the buffy coat.
• B. Break the hematocrit tube just below the buffy coat.
• C. Draw plasma directly from the vein.
• D. Remove the buffy coat and collect the plasma.

Answer: (A)

After centrifugation, plasma forms the top layer, with the buffy coat in the middle and red blood cells at the bottom. For a TP measurement, you want the clean plasma without cellular contamination. Break the hematocrit tube just above the buffy coat so the plasma can be expelled into a new container while the buffy coat and cells stay below. Breaking just below the buffy coat would pull buffy coat into the plasma, contaminating it and skewing results. Drawing plasma from a vein or removing the buffy coat from the tube aren’t the correct methods for obtaining pure plasma from this tube.