Risk of a first venous thrombotic event in carriers of a familial thrombophilic defect. The European Prospective Cohort on Thrombophilia (EPCOT).
BACKGROUND
Reliable risk estimates for venous thrombosis in families with inherited thrombophilia are scarce but necessary for determining optimal screening and treatment policies.


OBJECTIVE
In the present analysis, we determined the risk of a first venous thrombotic event in carriers of a thrombophilic defect (i.e. antithrombin-, protein C- or protein S deficiency, or factor V Leiden).


METHODS
The asymptomatic carriers had been tested prior to this study in nine European thrombosis centers because of a symptomatic carrier in the family, and were followed prospectively for 5.7 years on average between March 1994 and January 2001. Annually, data were recorded on the occurrence of risk situations for venous thrombosis and events (e.g. venous thrombosis, death).


RESULTS
Twenty-six of the 575 asymptomatic carriers (4.5%) and seven of the 1118 controls (0.6%) experienced a first deep venous thrombosis or pulmonary embolism during follow-up. Of these events, 58% occurred spontaneously in the carriers compared with 43% in the controls. The incidence of first events was 0.8% per year (95% CI 0.5-1.2) in the carriers compared with 0.1% per year (95% CI 0.0-0.2) in the controls. The highest incidence was associated with antithrombin deficiency or combined defects, and the lowest incidence with factor V Leiden.


CONCLUSIONS
The incidence of venous events in asymptomatic individuals from thrombophilic families does not exceed the risk of bleeding associated with long-term anticoagulant treatment in the literature (1-3%).
Vossen
C Y
CY
Department of Clinical Epidemiology, Leiden University Medical Center, Leiden, the Netherlands.
Conard
J
J
Fontcuberta
J
J
Makris
M
M
VAN DER Meer
F J M
FJ
Pabinger
I
I
Palareti
G
G
Preston
F E
FE
Scharrer
I
I
Souto
J C
JC
Svensson
P
P
Walker
I D
ID
Rosendaal
F R
FR
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D020152:Antithrombin III Deficiency; D016022:Case-Control Studies; D002648:Child; D002675:Child, Preschool; D005165:Factor V; D005192:Family Health; D005260:Female; D005500:Follow-Up Studies; D020022:Genetic Predisposition to Disease; D006801:Humans; D015994:Incidence; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D020151:Protein C Deficiency; D018455:Protein S Deficiency; D012306:Risk; D019851:Thrombophilia / Q000150:complications / Q000453:epidemiology / Q000235:genetics*; D020246:Venous Thrombosis / Q000453:epidemiology* / Q000209:etiology / Q000235:genetics*
C095381:factor V Leiden; D005165:Factor V