Table 1.

—[Introduction] Structured Clinical Questions

Population	Intervention(s)	Comparator	Outcome	Methodology
Hospitalized acutely ill medical patients	Mechanical prophylaxis (GCS, IPC, IVC filter) and/or pharmacologic prophylaxis (ASA, LDUH, LMWH, fondaparinux, VKA, oral DTI, oral direct Xa inhibitors)	No treatment, placebo, mechanical prophylaxis, and/or pharmacologic prophylaxis	Symptomatic DVT and PE, death, major bleeding events, mechanical prophylaxis complications	RCTs
	LDUH bid	LDUH tid
	Extended-duration pharmacologic prophylaxis, after initial short-duration prophylaxis	Short-duration prophylaxis
	Any screening for asymptomatic VTE with ultrasound	No screening
All patients admitted to a critical care unit	Routine screening with ultrasound for asymptomatic VTE	No screening	Symptomatic DVT, PE, death, major bleeding events	RCTs and observational studies
	LMWH, LDUH	No treatment, placebo, mechanical prophylaxis, and/or pharmacologic prophylaxis	Symptomatic DVT and PE, death, major bleeding events, mechanical prophylaxis complications	RCTs and observational studies
Patients with cancer
Receiving cancer treatment in outpatient setting	Mechanical prophylaxis (GCS) and/or pharmacologic prophylaxis (ASA, LDUH, LMWH, fondaparinux, VKA, oral DTI, oral direct Xa inhibitors)	No treatment, placebo, mechanical prophylaxis, and/or pharmacologic prophylaxis	Symptomatic DVT and PE, death, major bleeding events, mechanical prophylaxis complications	RCTs and observational studies
With indwelling central venous catheters	Pharmacologic prophylaxis (ASA, LDUH, LMWH, fondaparinux, VKA, oral DTI, oral direct Xa inhibitors)	No treatment, placebo, or pharmacologic prophylaxis	Symptomatic DVT and PE, death, major bleeding events, catheter failure	RCTs and observational studies
Chronically immobilized patients (e.g. nursing home or rehab residents, immobilized persons living at home)	Mechanical prophylaxis (GCS) and/or pharmacologic prophylaxis (ASA, LDUH, LMWH, fondaparinux, VKA, oral DTI, oral direct Xa inhibitors)	No treatment, placebo, mechanical prophylaxis, and/or pharmacologic prophylaxis	Symptomatic DVT and PE, death, major bleeding events, mechanical prophylaxis complications	RCTs and observational studies
Long-distance travelers	GCS, LMWH, ASA	No treatment, placebo, mechanical prophylaxis, and/or pharmacologic prophylaxis	Symptomatic DVT, PE, death, major bleeding events	RCTs and observational studies
All patients	Prognostic factors associated with risk of VTE	N/A	Symptomatic DVT and PE, death from PE	RCTs and observational studies
All patients	Prognostic factors associated with risk of bleeding	N/A	Major bleeding events, death from bleeding	RCTs and observational studies
Asymptomatic persons with thrombophilia (inherited thrombophilia, LAC, APLA)	Mechanical prophylaxis (GCS) and/or pharmacologic prophylaxis (ASA, LDUH, LMWH, VKA)	No treatment or placebo	Symptomatic DVT, PE, death, major bleeding events	RCTs and observational studies
Asymptomatic persons (ie, no previous VTE)	Statins	No treatment or placebo	Symptomatic DVT, PE, death	RCTs and observational studies

For tradeoff of benefits and harms, only symptomatic VTE events are considered. APLA = antiphospholipid antibodies; ASA = acetylsalicylic acid; DTI = direct thrombin inhibitor; GCS = graduated compression stockings; IPC = intermittent pneumatic compression; IVC = inferior vena cava; LAC = lupus anticoagulant; LDUH = low-dose unfractionated heparin; LMWH = low-molecular-weight heparin; PE = pulmonary embolism; RCT = randomized controlled trial; VKA = vitamin K antagonist.