Testing of Secondary Hemostasis Flashcards

1
Q

Prothrombin time or protime (PT)

A

Performed by adding tissue thromboplastin to pt’s plasma.

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2
Q

PT is a screen for

A

Inherited or acquired deficiencies in the extrinsic and common pathways.

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3
Q

PT measures Factors

A

I, II, V, VII, and X

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4
Q

PT reference range

A

10-13 sec

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5
Q

PT procedure

A

Specimen and reagents must be prewarmed to 37 Celsius.

Pt plasma added to thromboplastin reagent (contains calcium)

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6
Q

PT monitors oral anticoagulant therapy

A

Coumadin and Warfarin

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7
Q

INR: International normalized ratio

A

Used to correct for differences in coagulation instruments, reagents, etc.
INR is a calculation and is reported with ALL PT results.

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8
Q

PT sources of error

A

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

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9
Q

Activated Partial Thromboplastin Time (APTT)

A

Performed by adding plt phospholipid substitute and contact activator (APTT reagent) and calcium to activate factor XII.

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10
Q

APTT is a screen for

A

Intrinsic and common pathways

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11
Q

APTT measures all factors except

A

VII (extrinsic pathway) and XIII

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12
Q

APTT reference range

A

28-35 sec

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13
Q

APTT procedure

A

Reagents and specimens pre-warmed

pt plasma added to phospholipid activator and then CaCl2 is added.

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14
Q

APTT monitors IV/injection anticoagulant therapt

A

Heparin

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15
Q

APTT sources of error

A

Same as PT

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16
Q

Activated Clotting Time (ACT)

A

Used to monitor the effectiveness of high dose heparin therapy.

17
Q

ACT reference range

A

70-180 sec

18
Q

Thrombin Clotting Time (TCT) (TT)

A

Measures clotting time of the last step of the coagulation cascade, which is the conversion of fibrinogen into fibrin by thrombin.

19
Q

TCT is a test of which pathway?

A

The common pathway specifically fibrinogen.

  • Not commonly used to monitor anticoagulants.
  • Used to detect dysfibrinogenemia which is associated with hereditary factor deficiency, DIC, and liver disease.
20
Q

TCT Procedure

A

prewarm reagents and plasma, add pt plasma to thromin

21
Q

TCT reference range

A

10-16 sec

*Can be falsely prolonged due to heparin.

22
Q

Reptilase Time

A

Clotting similar to thrombin time except snake venom is used instead of thrombin.

23
Q

Reptilase Time reference range

A

18-22 sec

*NOT prolonged by heparin

24
Q

Fibrinogen Assay

A

Recommended test for estimating fibrinogen level.
Thrombin reagent is 25x more concentrated than in TCT.
Pt’s plasma is diluted.

25
Q

Fibrinogen Assay reference range

A

200-400 mg/dL

26
Q

Decreased fibrinogen

A

Liver disease, DIC

27
Q

Increased fibrinogen

A

Inflammatory disease, pregnancy

28
Q

APTT: Normal
PT: Abnormal

A
  1. Factor deficiency in extrinsic pathway (probably VII)

2. Specific factor inhibitor

29
Q

APTT: Abnormal
PT: Normal

A
  1. Factor deficiency in intrinsic pathway (XII, XI, kallikrein, IX, or VIII)
  2. Specific factor inhibitor
  3. Lupus anticoagulant
30
Q

APTT: Abnormal
PT: Abnormal
TCT: Normal

A
  1. Factor deficiency in common pathway
  2. Vitamin K deficiency
  3. Liver disease (multiple factor abnormalities)
  4. Inhibitor present
31
Q

APTT: Abnormal
PT: Abnormal
TCT: Abnormal

A
  1. Factor deficiency (I-fibrinogen)
  2. Severe liver disease
  3. DIC
  4. Inhibitor
32
Q

Mixing Study

A

If PT and/or APTT is prolonged, mixing studies are performed to differentiate factor deficiency from the presence of a circulating inhibitor.
*This procedure will correct the prolonged PT or APTT if it is caused by a deficiency of one or more of the coagulation factors.

33
Q

Mixing Study Procedure Part I

A
  1. pt plasma mixed with normal plasma
  2. APTT or PT performed
  3. If normal (corrected) then factor deficiency is suspected. If not normal, suspect inhibitor
34
Q

Mixing Study Procedure Part II

A
  1. Since some inhibitors react slowly you must prewarm the abnormal pt plasma and normal plasma for 2 hours at 37.
  2. Rerun APTT and PT on warmed plasma dilution
  3. If APTT still normal (corrected) it is probably caused by a factor deficiency.
    * Now you must perform specific factor assays.
35
Q

Immediate PT and APTT after Mixing Study: Correction

2 hour incubation PT and APTT: Correction

A

Factor Deficiency

36
Q

Immediate PT and APTT after Mixing Study: No Correction

2 hour incubation PT and APTT: No Correction

A

Lupus-like anticoagulant

37
Q

Immediate PT and APTT after Mixing Study: Correction

2 hour incubation PT and APTT: NO Correction

A

Specific Inhibitor (Factor VIII)

38
Q

Factor Assay

A

Performed to confirm a specific factor deficiency and to determine the actual activity of that factor within the plasma.
*Basis of a factor assay is the ability of the pts plasma to correct a prolonged PT or APTT of a known factor deficient plasma.

39
Q

Factor Assay ranges

A

Normal: 50-100%

Symptoms are evident at activity levels of 30% or less.