Identifying unprovoked thromboembolism patients at low risk for recurrence who can discontinue anticoagulant therapy.
BACKGROUND
Whether to continue oral anticoagulant therapy beyond 6 months after an "unprovoked" venous thromboembolism is controversial. We sought to determine clinical predictors to identify patients who are at low risk of recurrent venous thromboembolism who could safely discontinue oral anticoagulants.


METHODS
In a multicentre prospective cohort study, 646 participants with a first, unprovoked major venous thromboembolism were enrolled over a 4-year period. Of these, 600 participants completed a mean 18-month follow-up in September 2006. We collected data for 69 potential predictors of recurrent venous thromboembolism while patients were taking oral anticoagulation therapy (5-7 months after initiation). During follow-up after discontinuing oral anticoagulation therapy, all episodes of suspected recurrent venous thromboembolism were independently adjudicated. We performed a multivariable analysis of predictor variables (p < 0.10) with high interobserver reliability to derive a clinical decision rule.


RESULTS
We identified 91 confirmed episodes of recurrent venous thromboembolism during follow-up after discontinuing oral anticoagulation therapy (annual risk 9.3%, 95% CI 7.7%-11.3%). Men had a 13.7% (95% CI 10.8%-17.0%) annual risk. There was no combination of clinical predictors that satisfied our criteria for identifying a low-risk subgroup of men. Fifty-two percent of women had 0 or 1 of the following characteristics: hyperpigmentation, edema or redness of either leg; D-dimer > or = 250 microg/L while taking warfarin; body mass index > or = 30 kg/m(2); or age > or = 65 years. These women had an annual risk of 1.6% (95% CI 0.3%-4.6%). Women who had 2 or more of these findings had an annual risk of 14.1% (95% CI 10.9%-17.3%).


CONCLUSIONS
Women with 0 or 1 risk factor may safely discontinue oral anticoagulant therapy after 6 months of therapy following a first unprovoked venous thromboembolism. This criterion does not apply to men.
Rodger
Marc A
MA
Thrombosis Program, Division of Hematology, Department of Medicine, University of Ottawa, Ottawa, Ont. mrodger@ohri.ca
Kahn
Susan R
SR
Wells
Philip S
PS
Anderson
David A
DA
Chagnon
Isabelle
I
Le Gal
Grégoire
G
Solymoss
Susan
S
Crowther
Mark
M
Perrier
Arnaud
A
White
Richard
R
Vickars
Linda
L
Ramsay
Tim
T
Betancourt
Marisol T
MT
Kovacs
Michael J
MJ
D000284:Administration, Oral; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000925:Anticoagulants / Q000008:administration & dosage*; D000075202:Contraindications; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D011446:Prospective Studies; D012008:Recurrence; D012307:Risk Factors; D013997:Time Factors; D016896:Treatment Outcome; D054556:Venous Thromboembolism / Q000175:diagnosis / Q000188:drug therapy*
D000925:Anticoagulants