Unprovoked recurrent venous thrombosis: prediction by D-dimer and clinical risk factors.
BACKGROUND
The aim of the study was to determine the predictive value of D-dimer measurement for unprovoked recurrent venous thrombosis and the influence of sex, age and type of first event (unprovoked or provoked).


METHODS
Prospective cohort study of 272 patients with a first episode of venous thrombosis that was unprovoked or provoked by a non-surgical trigger.


RESULTS
The cumulative rate of unprovoked recurrence in patients with a positive D-dimer was 20% at 5 years [5.5/100 patient-years, 95% confidence interval (CI) 3.7-7.8] and in patients with a negative D-dimer 17% (4.1/100 patient-years, 95% CI 2.3-6.9). The rates are not different (hazard ratio 1.3, 95% CI 0.7-2.5). After adjustment for clinical risk factors a positive D-dimer result was significantly associated with an increased risk of unprovoked recurrent thrombosis (hazard ratio 2.0, 95% CI 1.01-3.9). The strongest indicator of risk of recurrence was male sex (hazard ratio 3.3 unadjusted and 2.9 after adjustment). The only determinant of D-dimer in a linear regression model was age (P < 0.001).


CONCLUSIONS
The analysis indicates that clinical risk factors confound the association between D-dimer and risk of recurrence and when adjusted for these confounders a positive D-dimer result is significantly associated with unprovoked recurrence. The clinical utility of D-dimer measurement in individual patients should be interpreted in conjunction with clinical risk factors.
Baglin
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Department of Haematology, Addenbrooke's Hospital, Cambridge University Hospital NHS Foundation Trust, Cambridge, UK. trevor.baglin@addenbrookes.nhs.uk
Palmer
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Luddington
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Baglin
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D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000925:Anticoagulants / Q000627:therapeutic use; D015986:Confounding Factors, Epidemiologic; D003277:Contraceptives, Oral, Combined; D003278:Contraceptives, Oral, Hormonal; D000075202:Contraindications; D017984:Enoxaparin / Q000627:therapeutic use; D005260:Female; D005338:Fibrin Fibrinogen Degradation Products / Q000032:analysis*; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011446:Prospective Studies; D012008:Recurrence; D012307:Risk Factors; D053828:Stockings, Compression; D013924:Thrombophlebitis / Q000097:blood / Q000453:epidemiology / Q000628:therapy; D020246:Venous Thrombosis / Q000097:blood / Q000188:drug therapy / Q000453:epidemiology* / Q000517:prevention & control
D000925:Anticoagulants; D003277:Contraceptives, Oral, Combined; D003278:Contraceptives, Oral, Hormonal; D017984:Enoxaparin; D005338:Fibrin Fibrinogen Degradation Products; C036309:fibrin fragment D