**Question:** All are components of cryoprecipitate except:

A. Antithrombin III
B. Fibronectin
C. Factor VIII
D. Factor XIII

**Core Concept:** Cryoprecipitate is a plasma product prepared by the freezing and thawing of plasma. During this process, certain proteins precipitate out of solution and can be separated as a concentrate for clinical use. These proteins include factors VIII, IX, XI, and XII, as well as von Willebrand factor, fibronectin, and antithrombin III.

**Why the Correct Answer is Right:** D. Factor XIII is not present in cryoprecipitate because it is not included in the freezing and thawing process. Cryoprecipitate is specifically prepared from pooled human plasma to concentrate coagulation factors, not all plasma proteins.

**Why Each Wrong Option is Incorrect:**

A. Antithrombin III (ATIII) is a plasma protein involved in the inhibition of coagulation. While ATIII is not included in cryoprecipitate, it is present in fresh frozen plasma (FFP), which is another plasma product used in transfusion therapy.

B. Fibronectin is a glycoprotein that plays a role in cell adhesion, wound healing, and immune response. Although it is present in plasma, it is not specifically concentrated in cryoprecipitate. Fibronectin can be found in other plasma products like fresh frozen plasma (FFP) and platelet concentrate.

C. Factor VIII is a clotting factor involved in the intrinsic pathway of coagulation. Factor VIII is part of cryoprecipitate, as it is one of the coagulation factors concentrated during the freezing and thawing process.

D. Factor XIII (FXIII) is a clotting factor involved in cross-linking fibrin chains during fibrin clot formation. FXIII is not included in cryoprecipitate because it is not a coagulation factor that precipitates during the freezing process. FXIII is present in fresh frozen plasma (FFP), another plasma product used for blood component therapy.

E. Factor XII is a clotting factor involved in the contact activation pathway. Factor XII is not specifically concentrated in cryoprecipitate, as it is not a coagulation factor that precipitates during the freezing process. Factor XII can be found in fresh frozen plasma (FFP) and platelet concentrate.

**Core Concept:** Cryoprecipitate is a plasma product derived from frozen plasma, which is used to replace clotting factors in patients with severe deficiencies or abnormalities of coagulation factors. The freezing process concentrates the coagulation factors that precipitate, leaving out other plasma proteins like fibronectin, antithrombin III, and factor XIII.

**Why Each Wrong Option is Incorrect:**

A. Fibronectin is a plasma glycoprotein involved in wound healing, immune response, and cell adhesion. While fibronectin is present in plasma, it is not specifically concentrated in cryoprecipitate because it is not a clotting factor that precipitates during the freezing process.