Integrated Billing and Coding Practice Test 2026 - Free Billing and Coding Practice Questions and Study Guide

Differentiating serum from plasma hinges on what happens to clotting factors during coagulation. When blood is allowed to clot, fibrinogen is converted into fibrin to form the clot, and the liquid portion that remains after removing the clot is serum. Because fibrinogen (and other clotting factors) are consumed in that process, serum does not contain fibrinogen. Plasma, on the other hand, is obtained from blood drawn with an anticoagulant, so it stays liquid and still contains fibrinogen and the other clotting factors. This is why serum is described as plasma without fibrinogen.