Types of studies

We included randomised controlled trials (RCTs). If we had found no trials of this sort, we would also have considered controlled clinical trials (CCTs). We excluded case reports, case series, and retrospective studies. We applied no limitation on the language of publication or country.

Types of participants

People of any age undergoing elective repair of an AAA.

Types of interventions

Laparoscopic repair (total laparoscopic repair or hand‐assisted laparoscopic repair) compared with either open surgical repair or EVAR.

We considered the following comparisons.

1. Laparoscopic repair (total or hand‐assisted laparoscopic repair) versus open surgical repair.

2. Laparoscopic repair (total or hand‐assisted laparoscopic repair) versus EVAR.

Types of outcome measures

Electronic searches

The Cochrane Vascular Information Specialist (CIS) searched the following databases for relevant trials:

• The Cochrane Vascular Specialised Register (searched 10 August 2016).

• The Cochrane Central Register of Controlled Trials (CENTRAL; 2016, Issue 7) in the Cochrane Library (searched 10 August 2016).

See Appendix 1 for details of the search strategy used to search CENTRAL.

The Cochrane Vascular Specialised Register is maintained by the CIS and is constructed from weekly electronic searches of MEDLINE Ovid, Embase Ovid, CINAHL, AMED, and through handsearching relevant journals. The full list of the databases, journals and conference proceedings which have been searched, as well as the search strategies used, are described in the Specialised Register section of the Cochrane Vascular module in the Cochrane Library (www.cochranelibrary.com).

The CIS searched the following trial registries (10 August 2016) for details of ongoing and unpublished studies using the terms 'laparoscopic AND aneurysm';

• ClinicalTrials.gov (www.clinicaltrials.gov).

• World Health Organization International Clinical Trials Registry Platform (www.who.int/trialsearch).

• ISRCTN Register (www.isrctn.com/).

See Appendix 2 for details of the search strategies used.

Searching other resources

We searched citations within identified studies. We planned, if needed, to contact authors of relevant papers by email to identify any unpublished randomised controlled trials.

Selection of studies

Two review authors (LR, SN) independently reviewed the results of all searches to identify potentially eligible articles. The two review authors (LR, SN) discussed each study to confirm eligibility for inclusion in the systematic review, excluding those not fulfilling the criteria as described in Criteria for considering studies for this review and stating the reasons for exclusion in the review.

Data extraction and management

Two review authors (LR, SN) independently extracted from each study information about the study characteristics, participants, interventions, duration of follow‐up, and outcome parameters using standardised forms. We extracted data on the following items, where available.

1. Study design.

2. Number of study participants.

3. Details of participants, including age, sex, diameter of AAA, diagnosis (clinical or ultrasound), and presence of co‐morbidities.

4. Stratification of low‐ and high‐risk patients defined by co‐morbidities, Vascular Physiological and Operative Severity Score for the enUmeration of Mortality and Morbidity (V(p)‐Possum) or Glasgow Aneurysm Score (GAS) where appropriate.

5. Interventions, including type of repair, adverse events (major and minor), and length of hospital stay.

6. Outcome measures as stated above.

7. Length of follow‐up.

Assessment of risk of bias in included studies

Two review authors (LR, SN) independently assessed the design and execution of each study according to the following criteria: random sequence generation; allocation concealment of treatment; blinding of participants, personnel, and outcomes; incomplete outcome data; selective outcome reporting; and other sources of bias in accordance with Cochrane's tool for assessing risk of bias (Higgins 2011). We judged the studies as either low risk of bias, high risk of bias, or unclear (due to either lack of information or uncertainty over the potential for bias). We resolved any disagreements by consensus between the two review authors.

Measures of treatment effect

We assessed dichotomous data using risk ratios (RRs) with 95% confidence intervals (CIs). We analysed continuous outcomes using mean differences (MDs) with 95% CIs where the scales were the same; and where scales were different but outcome measured was the same, we planned to use the standardised mean difference (SMD) with 95% CIs.

Unit of analysis issues

We did not include cross‐over trials. The individual participant was the unit of analysis.

Dealing with missing data

Where information was missing, we contacted the authors of the relevant study. If unsuccessful, we planned to exclude the data from the meta‐analysis but report it in the review. We intended to include outcome measures in this systematic review only if it was the intention of the study authors to perform the necessary assessments in all randomised participants. When fewer than 50% of the participants in a study had an acceptable follow‐up for a particular outcome measure, we planned on not reporting the results of this outcome measure due to the associated high risk of attrition bias.

Assessment of heterogeneity

It was intended that if the included studies were comparable with regard to age, sex, treatment, and used outcome definitions, we would perform a pooled analysis. We planned on assessing heterogeneity with the use of forest plots; and by a formal statistical test for heterogeneity, the I² statistic. Substantial heterogeneity was defined as I² greater than 50% (Higgins 2011). We planned on exploring possible causes of heterogeneity and taking appropriate measures.

Assessment of reporting biases

If more than 10 studies had been included in a meta‐analysis, we would have constructed a funnel plot to graphically ascertain the existence of publication bias (Higgins 2011).

Data synthesis

We entered the data into the Cochrane Review Manager 5 software (Review Manager 2014), and analysed them according to the guidelines of the Cochrane Handbook for Systematic Reviews of Interventions (Higgins 2011). We planned to use a fixed‐effect model where no substantial heterogeneity was found and a random‐effects model if heterogeneity (I² greater than 50%) was found.

Subgroup analysis and investigation of heterogeneity

We planned on performing subgroup analysis according to the following.

• Age.

• Gender.

• Body mass index > 30 kg/m².

• Diabetes.

• Type of laparoscopic repair (total or hand‐assisted).

• Previous cardiopulmonary co‐morbidities such as ischaemic heart disease, myocardial infarction, or chronic obstructive pulmonary disease (COPD) as determined by a preoperative cardiopulmonary exercise test (CPEX).

• Participants at high risk of complications, identified where possible using well‐validated and reliable scoring systems such as the GAS, V(p)‐Possum, or other tests.

We intended to examine heterogeneity for these by visual inspection of forest plots and the I² test.

Sensitivity analysis

We planned on performing a sensitivity analysis by excluding studies at high risk of selection, performance, detection, attrition, and reporting bias.