Which test is typically prolonged by heparin therapy?

Which test is typically prolonged by heparin therapy?

• A. D-Dimer
• B. Thrombin Time
• C. Fibrinogen
• D. Reptilase Time

Answer: (B)

Heparin works by blocking thrombin, so any test that depends on thrombin activity to form a final product will be prolonged when heparin is present. The Thrombin Time measures how long it takes for thrombin to convert fibrinogen into fibrin after adding a fixed amount of thrombin to plasma. If thrombin is inhibited by heparin, this conversion slows down, and the time is lengthened. That makes the Thrombin Time sensitive to heparin therapy and the test that’s typically prolonged under its influence. D-Dimer is a marker of fibrin breakdown, not a time-based clotting process, so it isn’t prolonged by heparin in the way a thrombin-dependent assay is. Fibrinogen level is a quantitative measure of a plasma protein, not a clotting time, so it isn’t directly prolonged by heparin. Reptilase Time uses a thrombin-like enzyme that isn’t inhibited by heparin, so it does not show prolongation with heparin therapy; it can help distinguish heparin effects from true fibrinogen abnormalities.

Heparin works by blocking thrombin, so any test that depends on thrombin activity to form a final product will be prolonged when heparin is present. The Thrombin Time measures how long it takes for thrombin to convert fibrinogen into fibrin after adding a fixed amount of thrombin to plasma. If thrombin is inhibited by heparin, this conversion slows down, and the time is lengthened. That makes the Thrombin Time sensitive to heparin therapy and the test that’s typically prolonged under its influence.

D-Dimer is a marker of fibrin breakdown, not a time-based clotting process, so it isn’t prolonged by heparin in the way a thrombin-dependent assay is. Fibrinogen level is a quantitative measure of a plasma protein, not a clotting time, so it isn’t directly prolonged by heparin. Reptilase Time uses a thrombin-like enzyme that isn’t inhibited by heparin, so it does not show prolongation with heparin therapy; it can help distinguish heparin effects from true fibrinogen abnormalities.