Ahmad 2021.

Study characteristics
Methods	Methods: single‐centre, prospective, randomised controlled, 2‐arm, parallel‐group, single‐blind (participants not blinded) Country: Egypt Duration: June 2019–December 2019
Participants	Number randomised: 150 (75 in each arm) Number analysed: 150 (100%) Mean age: experimental group: 41.8 (SD 9.4) years; control group: 37.6 (SD 8.7) years Sex (male/female): 15/135 Comorbidities DM: experimental group: 8; control group: 13 Hypertension: experimental group: 17; control group: 19 Mean bodyweight: not reported Mean BMI: experimental group 46.4 (SD 8.7) kg/m2; control group: 45.2 (SD 5.2) kg/m2 Bariatric surgery techniques Laparoscopic sleeve gastrectomy: 117 participants (78%); 49 in experimental group; 68 in control group Mini‐gastric bypass: 33 participants (22%); 20 in experimental group; 13 in control group Rationale for bariatric surgery indication: morbid obesity with repeated failure of weight loss after multidisciplinary medical treatment Inclusion criteria Primary bariatric procedures (sleeve gastrectomy and mini gastric bypass) Age 18–55 years Either sex Exclusion criteria History of congenital or acquired coagulation defects History of anticoagulant or antiplatelet medications for other disease Allergy to heparin and its derivatives History of HIT History of recent or old thromboembolism Postoperative complications such as bleeding and leak Symptomatic thromboembolism postoperatively Non‐compliance to therapy
Interventions	Experimental: mechanical thromboprophylaxis (perioperative elastic stockings on both lower limbs and early ambulation) combined with chemical thromboprophylaxis (enoxaparin 40 mg SC 12 hours preoperatively and every 24 hours postoperatively for 2 weeks) Control: mechanical thromboprophylaxis alone (perioperative elastic stockings on both lower limbs and early ambulation) Level of experience of the person carrying out the procedure: experienced Concomitant interventions: not reported Excluded medications: not reported
Outcomes	Primary (specified) DVT prophylaxis in person undergoing laparoscopic bariatric surgery, 4 weeks after surgery Primary (collected) Silent DVT, detected using duplex ultrasonography, 2 and 4 weeks after surgery Secondary outcomes (specified) Effect of combined prophylaxis method in prevention of DVT, 4 weeks after surgery Secondary outcomes (collected) Side effects of chemical prophylaxis (bleeding complications) in the immediate postoperative period and during chemical thromboprophylaxis (2 weeks) Time points reported: until 4 weeks after the procedure Cost of treatment: not reported
Funding source	Quote: "The authors received no financial support for the research, authorship, and/or publication of this article."
Declarations of interest of study authors	Quote: "The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article."
Notes	Protocol available (TCTR20200127002) Participants who experienced a VTE‐event were followed up for 6 months.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "An Excel sheet was used to create a randomization sequence with a 1:1 allocation using random block sizes of 2 and 4 by an independent doctor".
Allocation concealment (selection bias)	Low risk	Quote: "A researcher who was not included with the clinical trial determined the allocation of treatment by sequentially opening numbered, opaque, sealed envelopes".
Blinding of participants and personnel (performance bias)	Unclear risk	No method of blinding of participants or personnel was described.
Blinding of outcome assessment (detection bias)	Low risk	Quote: "The same person [the researcher that did the randomisation] was also responsible after the assignment to the interventions".
Incomplete outcome data (attrition bias)	Low risk	Quote: "No patient was withdrawn from the study after randomisation in addition to no changes to methods and outcomes after the commencement of the trial".
Selective reporting (reporting bias)	Low risk	All prespecified outcomes were reported.
Other bias	Low risk	We do not suspect any other bias related to this study.