CPT (Certified Phlebotomy Technician) Practice Exam

The correct answer highlights a fundamental distinction in the composition of plasma and serum. Plasma is the liquid component of blood that contains clotting factors, such as fibrinogen, along with other components like electrolytes, nutrients, hormones, and waste products. When blood clots, the clotting factors are consumed during the coagulation process, resulting in serum, which is essentially plasma devoid of these factors. This key difference is critical for understanding blood analysis and laboratory procedures, as serum is often used in various tests where the presence of clotting factors would interfere with the results.

The other options present misconceptions. One states that serum contains more nutrients than plasma, which is not accurate, as plasma typically has a higher concentration of various nutrients, given its role in transporting them. Another option claims there is no difference between the two; however, their definitions and functions in laboratory practices are distinctly different. Lastly, describing plasma as being thicker than serum is misleading because thickness can depend on other factors, such as temperature and viscosity, and this is not a typical way to differentiate between the two components. Understanding this distinction between plasma and serum is essential for phlebotomy technicians, especially when preparing samples for testing.