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Clotting tests

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					Clotting tests:
ONLY 30% of any factor (roughly) is needed for normal clotting to occur Mixing studies: 50%-50% pt plasma and normal plasma; recheck PT, aPTT – if normalized then there is factor deficiency TT (thrombin time) -> fibrinogen to fibrin time in seconds. Abnormal in fibrinogen deficiency/defect and heparin therapy PT (prothrombin time): pt’s plasma + Thromboplastin (TF) and Ca ++ -> factors I, II, V, VII, X (extrinsic pathway). Abnormal: above mentioned factor oops aPTT (activated partial thromboplastin time): pt’s plasma + Ca++ and phospholipid -> factors I, II, V, VIII, IX, X, XI, XII). Abnormal: decrease of any of those factor >50%. Lupus anticoagulant/Antiphospholipid antibody (antibodies against phospholipids): prolonged aPTT. Pt’s CLOT, test tube lies that they “bleed”. aPTT/dRVVT prolonged due to the Ab activity. Platelet naturalization (PNP) is normal. dRVVT (dilute Russell Viper Venom Test): direct activation of factor X by mixing with venom. The test is biphasic: 1 st very dilute reagent is given: will not correct lupus anticoagulant secondary to LA action on phospholipid. 2 nd more concentrated reagent is given (more phospholipid) which will overcome the presence of LA and clot. Congenital hemophilia vs. acquired (secondary to anti-factor antibody) Studies Congenital Acquired PTT Prolonged Prolonged Mixing studies Correction NO correction aPTT is prolonged in both hemophilia and lupus anticoagulant but in hemophilia pt bleeds and in lupus anticoagulant pt clots. Mixing studies will not likely correct aPTT in acquired hemophilia and in lupus anticoagulant. dRVVT will correct aPTT in acquired hemophilia but not in lupus anticoagulant (only after overload (titration to the antibody concentration) of phospholipid the test will correct aPTT).


				
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posted:1/12/2010
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