Vitamin K antagonists compared to placebo for prevention of venous thromboembolism following total hip or knee replacement or hip fracture repair
Patient or population: people requiring prevention of venous thromboembolism following total hip or knee replacement or hip fracture repair Setting: hospital and outpatient setting Intervention: vitamin K antagonists Comparison: placebo
Outcomes	Anticipated absolute effects* (95% CI)		Relative effect (95% CI)	Number of participants (studies)	Quality of the evidence (GRADE)	Comments
	Risk with placebo	Risk with vitamin K antagonists
Total VTE (symptomatic and asymptomatic) Treatment duration 28 ‐ 42 days	Study population		OR 0.10 (0.01 to 0.81)	360 (1 RCT)	⊕⊕⊕⊝ MODERATE 1	—
	51 per 1000	5 per 1000 (1 to 42)
Asymptomatic DVT Treatment duration 28 ‐ 42 days	see comment		—	—	—	not reported in single included study in this comparison
Asymptomatic proximal DVT Treatment duration 28 ‐ 42 days	see comment		—	—	—	not reported in single included study in this comparison
Asymptomatic distal DVT Treatment duration 28 ‐ 42 days	see comment		—	—	—	not reported in single included study in this comparison
All‐cause mortality Treatment duration 28 ‐ 42 days	see comment		—	360 (1 RCT)	—	single included study reported no deaths in either study arm so not possible to assess risk
Adverse events Treatment duration 28 ‐ 42 days	see comment		—	360 (1 RCT)	—	single included study reported no adverse events in either study arm so not possible to assess risk
Reoperation Treatment duration 28 ‐ 42 days	see comment		—	—	—	not reported in single included study in this comparison
Wound infection Treatment duration 28 ‐ 42 days	see comment		—	—	—	not reported in single included study in this comparison
Wound healing Treatment duration 28 ‐ 42 days	see comment		—	—	—	not reported in single included study in this comparison
*The risk in the intervention group (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI). CI: confidence interval; DVT: deep vein thrombosis; OR: odds ratio; PE: pulmonary embolism; RCT: randomised controlled trial; VTE: venous thromboembolism
GRADE Working Group grades of evidence High quality: We are very confident that the true effect lies close to that of the estimate of the effect Moderate quality: We are moderately confident in the effect estimate: The true effect is likely to be close to the estimate of the effect, but there is a possibility that it is substantially different Low quality: Our confidence in the effect estimate is limited: The true effect may be substantially different from the estimate of the effect Very low quality: We have very little confidence in the effect estimate: The true effect is likely to be substantially different from the estimate of effect