• What does aPTT measure?
• What disease can this be helpful in detecting?
• What is the use of aPTT in drug therapy?

• Measures the activity of the intrinsic coagulation pathway
• Can be used to detect deficient factors in two forms of hemophilia:

              Hemophilia A:  Factor VIII deficiency

              Hemophilia B:  Factor IX deficiency

• Used to monitor anticoagulant therapy w/unfractionated heparin

• Usually plasma will clot in 12-14 seconds after the administration of calcium + thromboplastin 
• Warfarin anti-coagulant therapy leads to an inactivation of factors VII, X, and thrombin (II) and prolongs the PT time.
• INR:  Used to normalize PT test results and monitor warfarin therapy

• Is a format for reporting prothrombin times (PT) of patients on warfarin 
• INR = [PT(Patient)/PT(Control)]^[isi]
• INR is derived by caculating a ratio of the patient's PT to the control PT and raising it to the power of the international sensitivity index 

1. Dilute thrombin added to patient's plasma and a control plasma
2. Clotting times are compared 
3. Since no Ca is added to the plasma, clotting time is ID of generation of thorombin and ONLY dependent on activity of exogenous thrombin 
4. Thrombin time can be increased if patient is on heparin b/c anti-thrombin activity is increased