Which laboratory test is used to investigate a hypercoagulable state?

• A. Thrombin time
• B. Reptilase time
• C. APCR
• D. Euglobulin lysis

Answer: (C)

Hypercoagulable states are about an increased tendency to form clots, often due to inherited thrombophilias. A common cause is Factor V Leiden, which makes factor V resistant to inactivation by activated protein C. The APCR test is designed to detect this resistance by measuring how much APC slows clot formation. In people with Factor V Leiden, the clotting time doesn’t lengthen as much when APC is present, indicating resistance. This direct assessment of APC resistance makes APCR the best test for investigating a hypercoagulable state.

Thrombin time and reptilase time focus on how quickly fibrin forms from fibrinogen and can be affected by fibrinogen abnormalities or anticoagulants, but they don’t specifically probe a predisposition to thrombosis. Euglobulin lysis time looks at fibrinolysis and clot breakdown, not the tendency to form clots in the first place.