In Case You Missed Tonight's LIVE: Recap
FREE LIVE STUDY SESSION EVENING📚🧪 - December 19 VIEW RECORDING - 162 mins (No highlights) Meeting Purpose Review the coagulation cascade and practice ASCP exam questions. Key Takeaways - Coagulation Cascade Basics: The intrinsic pathway (12, 11, 9, 8) handles internal vessel damage and is monitored by aPTT/PTT. The extrinsic pathway (3, 7) handles external tissue damage and is monitored by PT/INR. Both converge at the common pathway (10, 5, 2, 1). - Vitamin K-Dependent Factors: Factors II, VII, IX, and X require vitamin K for synthesis. Warfarin inhibits vitamin K, blocking these factors. Proteins C and S, natural anticoagulants, are also vitamin K-dependent. - Key Diagnostic Tests:Mixing Studies: Differentiate factor deficiencies (corrects) from inhibitors (does not correct).Bethesda Assay: Quantifies inhibitor strength after a mixing study indicates an inhibitor is present.Reptilase Time: Distinguishes heparin contamination (normal result) from a fibrinogen disorder (prolonged result) when thrombin time is prolonged. - Complex Concepts for Memorization:Lupus Anticoagulant (LA) Detection: Tests using low-phospholipid reagents (KCT, DRVVT, DTT) are more sensitive to LA because the antibody has fewer targets to bind, causing a larger effect.Time-Temperature-Dependent Inhibitors: These inhibitors (e.g., Factor VIII inhibitors) cause a mixing study to correct immediately, but then prolong again after incubation as the inhibitor activates. Topics Coagulation Cascade Fundamentals - Purpose: Form a blood clot to prevent hemorrhage. - Intrinsic Pathway (Internal Damage):Triggered by blood contact with a damaged vessel or foreign surface.Factors: XII → XI → IX → VIII.Monitored by: aPTT/PTT.Inhibited by: Heparin. - Extrinsic Pathway (External Damage):Triggered by tissue damage.Factors: III (Tissue Factor) → VII.Monitored by: PT/INR.Inhibited by: Warfarin. - Common Pathway:Convergence point for both pathways.Factors: X → V → II (Prothrombin) → IIa (Thrombin) → I (Fibrinogen) → Ia (Fibrin) → XIIIa (Stabilized Fibrin). - Vitamin K-Dependent Factors:Require vitamin K for synthesis: II, VII, IX, X.Proteins C and S (natural anticoagulants) are also vitamin K-dependent.Warfarin inhibits vitamin K, blocking these factors. - Factor XIII (Fibrin-Stabilizing Factor):Stabilizes the final fibrin clot.Deficiency is indicated by a clot dissolving in a 5 molar urea test.