Vitamin K antagonists compared to heparin 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: heparin
Outcomes	Anticipated absolute effects* (95% CI)		Relative effect (95% CI)	Number of participants (studies)	Quality of the evidence (GRADE)	Comments
	Risk with heparin	Risk with vitamin K antagonists
Total VTE (symptomatic and asymptomatic) Treatment duration 28 ‐ 42 days	Study population		OR 1.64 (0.85 to 3.16)	1279 (1 RCT)	⊕⊕⊝⊝ LOW 1 2	—
	23 per 1000	38 per 1000 (20 to 70)
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		OR 5.07 (0.24 to 105.83)	1279 (1 RCT)	⊕⊕⊝⊝ LOW 1 3	no cases of death reported in the heparin study arm
Adverse events Treatment duration 28 ‐ 42 days	see comment		—	—	—	not reported in single included study in this comparison
Reoperation Treatment duration 28 ‐ 42 days	Study population		OR 4.60 (0.99 to 21.38)	1279 (1 RCT)	⊕⊕⊝⊝ LOW 1 3	—
	3 per 1000	14 per 1000 (3 to 63)
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; VKA: vitamin K antagonist; 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