AACC Hematology & Coagulation 3

Question 1

Which combination of laboratory findings is most characteristic of disseminated intravascular coagulation (DIC)?

Accepted Answer

Decreased platelets, prolonged PT/aPTT, elevated D-dimer, decreased fibrinogen

Answer

DIC is characterized by simultaneous thrombosis and fibrinolysis, consuming platelets and clotting factors, producing thrombocytopenia, prolonged PT/aPTT, low fibrinogen, and elevated D-dimer from fibrin degradation.

Question 2

D-dimer is a specific fibrin degradation product measured in clinical laboratories. What is its primary clinical utility?

Accepted Answer

Ruling out venous thromboembolism (VTE) in low-probability patients

Answer

D-dimer has high sensitivity but low specificity for VTE; a negative result in a low-pretest-probability patient effectively rules out DVT or PE, avoiding the need for imaging.

Question 3

A ristocetin cofactor assay (VWF:RCo) is reduced and VWF antigen is also reduced. What is the most likely diagnosis?

Accepted Answer

Type 1 von Willebrand disease

Answer

Type 1 VWD, the most common form, shows a proportionate decrease in both VWF quantity (antigen) and function (ristocetin cofactor activity), typically to 20–50% of normal.

Question 4

A patient receiving streptokinase therapy for acute myocardial infarction will likely show which laboratory pattern?

Accepted Answer

Prolonged PT/aPTT, decreased fibrinogen, and elevated FDPs

Answer

Thrombolytic agents like streptokinase activate plasmin, which degrades fibrin and fibrinogen, resulting in prolonged PT/aPTT, decreased fibrinogen, and elevated fibrin degradation products.

Question 5

What is the normal platelet count reference range in adults?

Accepted Answer

150,000–400,000/μL

Answer

The normal adult platelet count is 150,000–400,000/μL; counts below 150,000/μL define thrombocytopenia, while counts above 400,000/μL define thrombocytosis.

AACC - American Association for Clinical Chemistry Certification Practice Test

AACC - American Association for Clinical Chemistry Certification Practice Test

AACC Hematology & Coagulation 3