Reference | Design | Comparison | Percentage with venous thrombosis history | Intervention | Control | Number of patient-years, intervention | Number of patient-years, control | Events, intervention | Events, control | Relative effect (95% CI) | Study quality |
Recurrent thrombosis | |||||||||||
Crowther e t al 200325 | RCT | Direct | 100 | Warfarin INR 3–4 | Warfarin INR 2–3 | 113 py | 119 py | 2.6/100 py | 0.8/100 py | HR 2.9 (0.3 to 28.0) | Low risk of bias* |
Finazzi e t al 200526 | RCT | Indirect | 68 | Warfarin INR 3–4.5 | Warfarin INR 2–3 | 189 py | 181 py | 3.1/100 py | 1.6/100 py | – | High risk of bias* |
Rosove and Brewer 199227 | Retrospective cohort | Indirect | 56 | Warfarin INR 3–4 | Warfarin INR 2–3 | 110.2 py | 40.9 py | 0 | 7/100 py | – | Intermediate quality |
Khamashta e t al 199528 | Retrospective cohort | Indirect | 54 | Warfarin ≥INR 3.0 | Warfarin INR <3.0 | 197.3 py | 141.3 py | 1.5/100 py | 23/100 py | – | High quality |
Ames e t al 200529 | Prospective cohort | Indirect | 74 | Warfarin INR 3–4 | Warfarin INR 2–3 | – | – | 10.5/100 py | 4.0/100 py | – | Intermediate quality |
Total | Direct and indirect | RR 0.67 (0.05 to 8.20), I2=82% | |||||||||
Major bleeding | |||||||||||
Crowther e t al 200325 | RCT | Direct | 100 | Warfarin INR 3–4 | Warfarin INR 2–3 | 111 py | 133 py | 2.7/100 py | 3.0/100 py | HR 1.0 (0.02 to 4.8) | Low risk of bias* |
Finazzi e t al 200526 | RCT | Indirect | 68 | Warfarin INR 3–4.5 | Warfarin INR 2–3 | 189 py | 181 py | 1.0/100 py | 1.6/100 py | – | High risk of bias* |
Khamashta e t al 199528 | Retrospective cohort | Indirect | 54 | Warfarin ≥3.0 | Warfarin <3.0 | 197.3 py | 141.3 py | 1.7/100 py | 0 | – | High quality |
Ames e t al 200529 | Prospective cohort | Indirect | 74 | Warfarin INR 3–4 | Warfarin INR 2–3 | – | – | 10.5/100 py | 0.57/100 py | – | Intermediate quality |
Direct and Indirect | RR 1.61 (0.34 to 7.56) I2=35% |
*Risk of bias for randomised controlled trials using the Cochrane tool.
INR, international normalised ratio; RCT, randomised controlled trial; py, person-years.