Thrombophilia laboratory findings: Difference between revisions

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{{Thrombophilia}}
{{Thrombophilia}}
{{CMG}}
{{CMG}} {{asiri}}
 
==Overview==
==Overview==
* There are specific [[Thrombophilia_laboratory_findings|laboratory findings]] associated with each inherited thrombophilias.
* Refer to page on [[screening]] for recommendations regarding thrombophilia testing.
==Laboratory Findings==
==Laboratory Findings==
===Indications for screening===
Routine screening is not indicated in those individuals with an obvious acquired cause. For example, if the thrombosis is due to immobilisation after recent [[orthopedic surgery]], it is unlikely that an underlying cause is found. Comprehensive testing in any patient should include complete assessment of risk factors and its effect on long-term therapy. Some of the indications of further testing may include<ref name="pmid19289024">{{cite journal |author=Foy P, Moll S |title=Thrombophilia: 2009 update |journal=Curr Treat Options Cardiovasc Med |volume=11 |issue=2 |pages=114–28 |year=2009 |month=April |pmid=19289024 |doi= |url=}}</ref><ref name="pmid11309638">{{cite journal |author=Seligsohn U, Lubetsky A |title=Genetic susceptibility to venous thrombosis |journal=N. Engl. J. Med. |volume=344 |issue=16 |pages=1222–31 |year=2001 |month=April |pmid=11309638 |doi=10.1056/NEJM200104193441607 |url=}}</ref>:
* Unexplained venous thromboembolism at an age of less than 50 years
* Recurrent spontaneous thrombosis
* Unusual sites like portal, splenic, mesenteric, hepatic or renal veins
* Family history in first-degree relatives
* Recurrent pregnancy losses<ref>Dawood, F., Farquharson, R., Quenby, S.''Recurrent miscarriage.'' Current Obstetrics & Gynaecology, 2004; 14:247-253.</ref>
* Recurrence of venous thromboembolism while adequately anticoagulated
* Warfarin-induced skin necrosis
* Unexplained arterial thromboembolism in a younger patient without significant arteriosclerosis risk factors and no cardioembolic source
===Timing===
===Timing===
The timing of tests is very important as it influences the levels of various thrombogenic factors in the body.
The timing of tests is very important as it influences the levels of various thrombogenic factors in the body.
Line 29: Line 22:
Tests for thrombophilia are categorized according to their priority, as discussed below:
Tests for thrombophilia are categorized according to their priority, as discussed below:


'''1. General tests:''' These include [[prothrombin time]], INR, and [[partial thromboplastin time]].
{| class="wikitable"
 
! style="font-weight: bold;" | Priority
'''2. High priority tests:''' 
! style="font-weight: bold;" | Timing
* Activated protein C resistance
! style="font-weight: bold;" | Test
* Factor V Leiden (Homozygosity or heterozygosity)
! style="font-weight: bold;" | Associated Diagnosis
* Prothrombin gene mutation (G20210A)
|-
* Homocysteine levels
| High
* Factor VIII
|
* Lupus anticoagulant
| Complete blood count
 
| General
'''3. Intermediate priority'''
|-
* Protein C activity
|
* Protein S activity
|
* Antithrombin activity
| Coagulation studies: INR, prothrombin time, partial thromboplastin time
* Anticardiolipin antibodies
| General
 
|-
'''4. Low priority'''
|
* Thrombin time
|
* Fibrinogen levels
| Factor V Leiden mutation studies
* Factor IX activity
| Factor V Leiden
* Factor X activity
|-
* [[MTHR]] gene
|
 
|
 
| Prothrombin 20210 gene mutation
 
| Prothrombin G20210A
* '''High priority and intermediate priority tests''' should be performed in those with an unprovoked thrombotic event and have a recurrent event, cerebral-or visceral thrombosis, stillbirth, three or more unexplained spontaneous abortions, family history of venous thrombosis, or are younger than 45 years.
|-
 
|
* '''High priority tests''' only should be conducted in those who have a first unprovoked event, age > 45 years, event provoked by pregnancy/puerperium/use of oral contraceptives or hormone-replacement therapy, proximal-vein thrombosis, pulmonary embolism, or both provoked by surgery, trauma, or immobilization.
|
| Lupus anticoagulant
| Antiphospholipid syndrome
|-
| Intermediate
|
| Anticardiolipin antibodies
| Antiphospholipid syndrome
|-
|
| Delay 6 months
| Functional assay for antithrombin (antithrombin-heparin co-factor assay)
| Antithrombin deficiency
|-
|
| Delay 6 months
| Protein C functional assay (preferred over plasma protein levels)
| Protein C deficiency
|-
|
| Delay 6 months
| Free protein S immunoassay
| Protein S deficiency
|-
|
|
| Factor VIII level (use c-reactive protein as control)
| Factor VIII disorders
|-
|
|
| Flow cytometry
| Paroxysmal nocturnal hemoglobinuria
|-
|
|
| Peripheral blood smear, JAK2 mutation studies
| Myeloproliferative disorders
|-
|
|
| Homocysteine level
| Hyperhomocysteinemia
|-
|
|
| Vitamin B12 level
| Hyperhomocysteinemia
|-
| Low
|
| Thrombin time
| General/Fibrinogen disorders
|-
|
|
| Fibrinogen level
| Fibrinogen disorders
|-
|
|
| Reptilase time
| General/Fibrinogen disorders
|-
|
|
| Plasminogen level
| Plasminogen disorders
|-
|
|
| Factor IX activity
| Factor IX disorders
|-
|
|
| Factor X activity
| Factor X disorders
|}


* It is recommended that all these patients be treated with anticoagulation for at least 6 months, unless contraindicated.
===Variability in thrombophilia testing===
* '''Warfarin''': Decreases protein C and S levels
* '''Heparin''': Decreases antithrombin activity and interferes with evaluation for antiphospholipid antibody
* '''Acute thrombosis''': Decreases antithrombin, protein C, and protein S levels


==References==
==References==

Revision as of 19:02, 29 June 2016


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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Asiri Ediriwickrema, M.D., M.H.S. [2]

Overview

  • There are specific laboratory findings associated with each inherited thrombophilias.
  • Refer to page on screening for recommendations regarding thrombophilia testing.

Laboratory Findings

Timing

The timing of tests is very important as it influences the levels of various thrombogenic factors in the body.

  • Testing at the time of acute venous thrombosis is not indicated or during ongoing anti-coagulation.
  • Best time to test is 4 weeks after completion of anticoagulation.
  • Avoid intercurrent severe illness
  • Pregnancy, oral contraceptives, hormone replacement therapy and cancer chemotherapy may also affect some tests.
  • Factor V Leiden and Prothrombin mutation can be done in patients on anticoagulants and even in acute phase, as these are PCR tests. However, other tests can be done only at a later stage to rule out two disorders.

Type of tests

Tests for thrombophilia are categorized according to their priority, as discussed below:

Priority Timing Test Associated Diagnosis
High Complete blood count General
Coagulation studies: INR, prothrombin time, partial thromboplastin time General
Factor V Leiden mutation studies Factor V Leiden
Prothrombin 20210 gene mutation Prothrombin G20210A
Lupus anticoagulant Antiphospholipid syndrome
Intermediate Anticardiolipin antibodies Antiphospholipid syndrome
Delay 6 months Functional assay for antithrombin (antithrombin-heparin co-factor assay) Antithrombin deficiency
Delay 6 months Protein C functional assay (preferred over plasma protein levels) Protein C deficiency
Delay 6 months Free protein S immunoassay Protein S deficiency
Factor VIII level (use c-reactive protein as control) Factor VIII disorders
Flow cytometry Paroxysmal nocturnal hemoglobinuria
Peripheral blood smear, JAK2 mutation studies Myeloproliferative disorders
Homocysteine level Hyperhomocysteinemia
Vitamin B12 level Hyperhomocysteinemia
Low Thrombin time General/Fibrinogen disorders
Fibrinogen level Fibrinogen disorders
Reptilase time General/Fibrinogen disorders
Plasminogen level Plasminogen disorders
Factor IX activity Factor IX disorders
Factor X activity Factor X disorders

Variability in thrombophilia testing

  • Warfarin: Decreases protein C and S levels
  • Heparin: Decreases antithrombin activity and interferes with evaluation for antiphospholipid antibody
  • Acute thrombosis: Decreases antithrombin, protein C, and protein S levels

References

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