Which of the Following Additives Is Preferred When Drawing Blood

Multiple Choice

Which of the following additives is preferred when drawing blood samples to measure parathyroid hormone (PTH) ?

A) Acid citrate dextrose because PTH is least stable using this additive
B) Potassium (3) -EDTA (K₃-EDTA) because PTH is most stable using this additive
C) Sodium citrate because PTH is most stable using this additive
D) Sodium fluoride/potassium oxalate because PTH will complex with oxalate to increase its stability