Vedovati 2014.

Methods	RCT, assessor‐blinded, compression ultrasonography.
Participants	Patients undergoing elective laparoscopic surgery for colorectal cancer.
Interventions	LMWH (enoxaparin 4000 IU in 79% allocated to extended prophylaxis, dalteparin 5000 IU in 21% allocated to extended prophylaxis, total treatment period 27 to 31 days).
Outcomes	LMWH 112 Control 113
Notes	LMWH prophylaxis medication varied prior to randomization to extended duration LMWH prophylaxis (enoxaparin 4000 UI or dalterparin 5000 UI or nadroparin 2850 IU). The study was interrupted after the results of the interim analysis showed a reduction in the rate of VTE in patients assigned to extended prophylaxis (P < 0.01). Compression ultrasonography day 26 to 30.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Centralized randomization, method not stated in manuscript.
Allocation concealment (selection bias)	Unclear risk	Unclear.
Blinding (performance bias and detection bias) All outcomes	Unclear risk	Compression ultrasonography evaluated by blinded investigator. Unclear if data‐analysts blinded.
Blinding of participants and personnel (performance bias) All outcomes	High risk	Patients and presumably caregivers not blinded.
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Terminated prematurely after interim analysis showed a reduction in the rate of VTE in patients assigned to extended prophylaxis.
Selective reporting (reporting bias)	Low risk	Intention‐to‐treat analysis on all patients with at least 26 days of follow up and at least one dose of medication; it appears all randomized patients met these parameters.
Other bias	Low risk	The study appears to be free of other sources of bias.

IPC: intermittent pneumatic compression; IU: international units: LMWH: low molecular weight heparin; RCT: randomized controlled trial; VTE: venous thromboembolism.