APTT

Causes of prolonged aPTTs: 1.Spurious (common to many Coag tests): – dilution (saline, Tx), underfilled specimen, clotted, prolonged tourniquet time – Heparin (therapeutic, SC, lines (esp ICU, dialysis), wrong tube for collection) – Polycythemia (Hct >45 causes citrate ratio to be incorrect) 2.Presence of an inhibitor. – lupus anticoagulant (LAC) - very common esp with Platelin LS reagent as LAC sensitive – VIII or other acquired inhibitor (rare except in Haemophilia centre or elderly patient) 3.Factor deficiency: – Congenital deficiency of 1/more intrinsic clotting factors or vWF (not FVII). – Severe Vitamin K deficiency (II, IX,X) or warfarin overanticoagulation – Liver disease (also reduces AT3, Prot C/S) – includes dys/hypofibrinogenaemia 4.DIC (FDP effect and factor consumption, including fibrinogen) % “normal population” have APTT > NR (by definition) 6.Excess LMWH or danaparoid (Xa activity >> IIa effect), hirudins Causes of shortened APTTs: 1.activated specimen/started to clot (esp NICU samples, check for clots, rebleed) 2.  FVIII (acute phase reactant) 3.delayed analysis UFH Tx patient specimen after collection (release of PF4 neutralises heparin) 4.2.5% pop have APTT <NR (by definition)

Coagulation FactorPlasma ConcentrationPlasma T1/2 Life Fibrinogen  g/ml80-90 hrs Prothrombin  g/ml60-70 hrs Factor V5-10  g/ml15-25 hrs Factor VII0.5  g/ml 4-7 hrs Factor VIII:C  g/ml8-16 hrs Factor IX3  g/ml12-24 hrs Factor X10-15  g/ml40-45 hrs Factor XI2-7  g/ml40-84 hrs Factor XII29-40  g/ml40-60 hrs Factor XIII20  g/ml120 hrs Prekallikrein25-45  g/mlapprox. 35 hrs HMWK70-90  g/ml hrs

PT / INR

Causes of high PT –liver disease –DIC –congenital deficiency: II, V, VII, X or fibrinogen (rare) –nephrotic syndromes (loss of clotting factors) –presence of an inhibitor (factor or rarely LAC) –poorly collected specimen eg. over-filled specimen under-filled specimen –vitamin K deficiency (eg diet/malabsorption) –warfarin –gross over-heparinization Shortened INR’S usually indicate activation of the specimen during collection by skin/traumatic venepuncture

FDPs INTRINSIC EXTRINSIC TCT Fibrinogen Clot Stability Test

TCT

LMWH et al. vs UFH fondaparinux pure anti-Xa SSSSSSSSS UFH >18 saccharide units with sulphonated tail- Xa:IIa 1:1 danaparoid - Xa:IIa 28:1 - not a heparin protamine LMWH mainly <18 saccharide units eg. enoxaparin - Xa:IIa 3.9:1 SSS

Fibrinogen