What reagent is used in APTT testing?

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Multiple Choice

What reagent is used in APTT testing?

APTT assesses the intrinsic coagulation pathway by triggering clotting in plasma through contact activation. The reagent used provides both a phospholipid surface and a contact activator, which together initiate the intrinsic pathway (factors XII, XI, IX, VIII) so the cascade can proceed once calcium is present. This combination—partial thromboplastin with an activator—is what drives the assay. Calcium is added separately to reverse the citrate anticoagulation, but by itself calcium chloride isn’t the reagent that starts the test. Thrombin alone would bypass the cascade, giving an uninformative result, and a factor IX supplement isn’t used as the standard reagent in this assay.

APTT assesses the intrinsic coagulation pathway by triggering clotting in plasma through contact activation. The reagent used provides both a phospholipid surface and a contact activator, which together initiate the intrinsic pathway (factors XII, XI, IX, VIII) so the cascade can proceed once calcium is present. This combination—partial thromboplastin with an activator—is what drives the assay. Calcium is added separately to reverse the citrate anticoagulation, but by itself calcium chloride isn’t the reagent that starts the test. Thrombin alone would bypass the cascade, giving an uninformative result, and a factor IX supplement isn’t used as the standard reagent in this assay.

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