Which statement about plasma collection for a blood chemistry analysis is false?

Which statement about plasma collection for a blood chemistry analysis is false?

• A. Keep the cap on the blood collection tube as much as possible to minimize evaporation.
• B. Remove the needle from the syringe before discharging the blood into a sample tube to minimize hemolysis.
• C. To separate, allow the sample to clot for approximately 30 minutes; gently remove the clot from the sides of the tube, centrifuge, and then remove the plasma.
• D. Avoid lipemia by fasting the animal before collecting the sample.

Answer: (C)

The essential idea is that plasma is obtained from blood that has not clotted, using an anticoagulant and then centrifuging to separate the liquid plasma from the cells. If you let the blood clot first, you’re creating serum, not plasma, so the described process would not yield plasma for a chemistry analysis. The statement describes allowing the sample to clot for about 30 minutes, then gently removing the clot, centrifuging, and removing the plasma. That sequence produces serum, because clot formation has already removed the clotting factors from the liquid. For plasma, you need to prevent clotting in the first place, collect with an anticoagulant, mix well, and then centrifuge to separate plasma while the anticoagulant remains present. The other practices align with proper plasma handling: keeping the cap on the tube to minimize evaporation, transferring blood with methods that reduce shear to lessen hemolysis, and fasting the animal to reduce lipemia that can interfere with many chemistry assays.

The essential idea is that plasma is obtained from blood that has not clotted, using an anticoagulant and then centrifuging to separate the liquid plasma from the cells. If you let the blood clot first, you’re creating serum, not plasma, so the described process would not yield plasma for a chemistry analysis.

The statement describes allowing the sample to clot for about 30 minutes, then gently removing the clot, centrifuging, and removing the plasma. That sequence produces serum, because clot formation has already removed the clotting factors from the liquid. For plasma, you need to prevent clotting in the first place, collect with an anticoagulant, mix well, and then centrifuge to separate plasma while the anticoagulant remains present.

The other practices align with proper plasma handling: keeping the cap on the tube to minimize evaporation, transferring blood with methods that reduce shear to lessen hemolysis, and fasting the animal to reduce lipemia that can interfere with many chemistry assays.