Testing of Secondary Hemostasis Flashcards
Prothrombin time or protime (PT)
Performed by adding tissue thromboplastin to pt’s plasma.
PT is a screen for
Inherited or acquired deficiencies in the extrinsic and common pathways.
PT measures Factors
I, II, V, VII, and X
PT reference range
10-13 sec
PT procedure
Specimen and reagents must be prewarmed to 37 Celsius.
Pt plasma added to thromboplastin reagent (contains calcium)
PT monitors oral anticoagulant therapy
Coumadin and Warfarin
INR: International normalized ratio
Used to correct for differences in coagulation instruments, reagents, etc.
INR is a calculation and is reported with ALL PT results.
PT sources of error
Blood Collection: TF in sample and premature activation of factor VII.
Sample Processing: Delay in testing which may decrease factor V.
Pt HCT: Increased hct=decreased plasma volume
*Plasma to anticoagulant ratio: 5:1
Activated Partial Thromboplastin Time (APTT)
Performed by adding plt phospholipid substitute and contact activator (APTT reagent) and calcium to activate factor XII.
APTT is a screen for
Intrinsic and common pathways
APTT measures all factors except
VII (extrinsic pathway) and XIII
APTT reference range
28-35 sec
APTT procedure
Reagents and specimens pre-warmed
pt plasma added to phospholipid activator and then CaCl2 is added.
APTT monitors IV/injection anticoagulant therapt
Heparin
APTT sources of error
Same as PT