American Society for Clinical Pathology (ASCP) Histotechnician Certification Practice Exam

A blood sample collected in a tube without anticoagulant would contain what?

1. Whole blood

2. Plasma

3. Serum

4. Coagulated blood

The correct answer is: Serum

When a blood sample is collected in a tube without anticoagulant, the blood undergoes a natural process of coagulation. As the blood clots, the gel-like substance that forms is essentially the clot itself, and the liquid portion that separates from this clot is referred to as serum. Serum is the component of blood that remains after coagulation has occurred and is free of clotting factors, as they become part of the clot. It contains proteins, electrolytes, hormones, and waste products. This distinction is important because it highlights the difference between plasma, which is the liquid component of whole blood that has not clotted and contains clotting factors, and serum, which is obtained post-coagulation. This fundamentally clarifies why serum is the correct answer when discussing a blood sample collected without any anticoagulant in the test tube.