Background
Description of the condition
Description of the intervention
How the intervention might work
Why it is important to do this review
Objectives
Methods
Criteria for considering studies for this review
Types of studies
Types of participants
Types of interventions
Types of outcome measures
Primary outcomes
Secondary outcomes
Exploratory outcomes
Search methods for identification of studies
Electronic searches
-
Cochrane Central Register of Controlled Trials (CENTRAL) in The Cochrane Library.
-
MEDLINE (Ovid, from 1946 onwards).
-
Embase (Ovid, from 1980 onwards).
-
Web of Science Core Collection (Thomson Reuters, from 1900 onwards)
-
BIOSIS (Thomson Reuters, from 1926 onwards)
-
LILACS (from 1982 onwards)
-
CINAHL (from 1937 onwards)
-
SCOPUS (from 1966 onwards)
Searching other resources
Data collection and analysis
Selection of studies
Data extraction and management
Assessment of risk of bias in included studies
Bias domains
Random sequence generation
-
Low risk of bias: sequence generation was achieved using computer random number generation or a random number table. Drawing lots, tossing a coin, shuffling cards and throwing dice were adequate if performed by an independent person not otherwise involved in the trial.
-
Unclear risk of bias: the method of sequence generation was not specified.
-
High risk of bias: the sequence generation method was not random or only quasi-randomised.
Allocation concealment
-
Low risk of bias: the allocation sequence was described as unknown to the investigators. Hence, the participants’ allocations could not have been foreseen in advance of, or during, enrolment. Allocation was controlled by a central and independent randomisation unit, an on-site locked computer, identical looking numbered sealed opaque envelopes, drug bottles or containers prepared by an independent pharmacist, or an independent investigator.
-
Unclear risk of bias: it was unclear if the allocation was hidden or if the block size was relatively small and fixed so that intervention allocations may have been foreseen in advance of, or during, enrolment.
-
High risk of bias: the allocation sequence was likely to be known to the investigators who assigned the participants.
Blinding of participants and treatment providers
-
Low risk of bias: it was described that both participants and treatment providers were blinded to treatment allocation.
-
Unclear risk of bias: it was unclear whether participants and treatment providers were blinded, or the extent of blinding was insufficiently described.
-
High risk of bias: no blinding or incomplete blinding of participants and treatment providers was performed.
Blinding of outcome assessment
-
Low risk of bias: it was mentioned that outcome assessors were blinded and this was described.
-
Unclear risk of bias: it was not mentioned whether the outcome assessors were blinded, or the extent of blinding was insufficiently described.
-
High risk of bias: no blinding or incomplete blinding of outcome assessors was performed.
Incomplete outcome data
-
Low risk of bias: missing data were unlikely to make intervention effects depart from plausible values. This could either be (1) there were no drop-outs or withdrawals; or (2) the numbers and reasons for the withdrawals and drop-outs for all outcomes were clearly stated and could be described as being similar in both groups, and the trial handled missing data appropriately in an intention-to-treat analysis using proper methods (e.g. multiple imputations). Generally, the trial was judged to be at a low risk of bias due to incomplete outcome data if drop-outs were less than 5%. However, the 5% cut-off was not definitive.
-
Unclear risk of bias: there was insufficient information to assess whether missing data were likely to induce bias on the results.
-
High risk of bias: the results were likely to be biased due to missing data either because the pattern of drop-outs could be described as being different in the two intervention groups or the trial used improper methods in dealing with the missing data (e.g. last observation carried forward).
Selective outcome reporting
-
Low risk of bias: a protocol was published before randomisation began and all outcome results were reported adequately. If there is no protocol or the protocol is published after the trial has begun, reporting of all-cause mortality and various types of serious adverse events will grant the trial a grade of ‘low risk of bias’ for this bias domain.
-
Unclear risk of bias: no protocol was published.
-
High risk of bias: the outcomes in the protocol were not reported on.
Other bias
-
Low risk of bias: the trial appeared to be free of other bias domains that could put it at risk of bias.
-
Unclear risk of bias: the trial may or may not have been free of other domains that could put it at risk of bias.
-
High risk of bias: there were other factors in the trial that could put it at risk of bias.
Overall risk of bias
Assessment of bias in conducting the systematic review
Measures of treatment effect
Unit of analysis issues
Dealing with missing data
Dichotomous outcomes
Continuous outcomes
Assessment of heterogeneity
Assessment of reporting biases
Data synthesis
Subgroup analysis and investigation of heterogeneity
Sensitivity analysis
Coronary artery bypass surgery compared with medical therapy alone for ischaemic heart disease | |||||
Patient or population: Adult patients with ischaemic heart disease Settings: Hospital Intervention: Coronary artery bypass surgery Comparison: Medical therapy | |||||
Outcomes
|
Illustrative comparative risks
a
(95% CI)
|
Relative effect (95% CI)
|
No of Participants (studies)
|
Quality of the evidence (GRADE)
| |
Assumed risk
|
Corresponding risk
| ||||
Medical therapy
|
Coronary artery bypass surgery
| ||||
All-cause mortality [follow-up] | Low risk population | RR [value] ([value] to [value]) | [value] ([value]) | ⊕⊝⊝⊝ very low ⊕⊕⊝⊝ low ⊕⊕⊕⊝ moderate ⊕⊕⊕⊕ high | |
[value] per 1000 | [value] per 1000 ([value] to [value]) | ||||
Medium risk population | |||||
[value] per 1000 | [value] per 1000 ([value] to [value]) | ||||
High risk population | |||||
[value] per 1000 | [value] per 1000 ([value] to [value]) | ||||
Serious adverse events [follow-up] | Low risk population | RR [value] ([value] to [value]) | [value] ([value]) | ⊕⊝⊝⊝ very low ⊕⊕⊝⊝ low ⊕⊕⊕⊝ moderate ⊕⊕⊕⊕ high | |
[value] per 1000 | [value] per 1000 ([value] to [value]) | ||||
Medium risk population | |||||
[value] per 1000 | [value] per 1000 ([value] to [value]) | ||||
High risk population | |||||
[value] per 1000 | [value] per 1000 ([value] to [value]) | ||||
Quality of life [follow-up] | The mean quality of life rating ranged across control groups from [value][measure] | The mean quality of life rating in the intervention groups was [value] [lower/higher] [(value to value lower/higher)] | [value] ([value]) | ||
Cardiovascular mortality [follow-up] | Low risk population | RR [value] ([value] to [value]) | [value] ([value]) | ⊕⊝⊝⊝ very low ⊕⊕⊝⊝ low ⊕⊕⊕⊝ moderate ⊕⊕⊕⊕ high | |
[value] per 1000 | [value] per 1000 ([value] to [value]) | ||||
Medium risk population | |||||
[value] per 1000 | [value] per 1000 ([value] to [value]) | ||||
High risk population | |||||
[value] per 1000 | [value] per 1000 ([value] to [value]) | ||||
Myocardial infarction [follow-up] | Low risk population | RR [value] ([value] to [value]) | [value] ([value]) | ⊕⊝⊝⊝ very low ⊕⊕⊝⊝ low ⊕⊕⊕⊝ moderate ⊕⊕⊕⊕ high | |
[value] per 1000 | [value] per 1000 ([value] to [value]) | ||||
Medium risk population | |||||
[value] per 1000 | [value] per 1000 ([value] to [value]) | ||||
High risk population | |||||
[value] per 1000 | [value] per 1000 ([value] to [value]) | ||||
Angina [follow-up] | The mean angina rating ranged across control groups from [value][measure] | The mean angina rating in the intervention groups was [value] [lower/higher] [(value to value lower/higher)] | [value] ([value]) | ⊕⊝⊝⊝ very low ⊕⊕⊝⊝ low ⊕⊕⊕⊝ moderate ⊕⊕⊕⊕ high | |
Stroke [follow-up] | Low risk population | RR [value] ([value] to [value]) | [value] ([value]) | ⊕⊝⊝⊝ very low ⊕⊕⊝⊝ low ⊕⊕⊕⊝ moderate ⊕⊕⊕⊕ high | |
[value] per 1000 | [value] per 1000 ([value] to [value]) | ||||
Medium risk population | |||||
[value] per 1000 | [value] per 1000 ([value] to [value]) | ||||
High risk population | |||||
[value] per 1000 | [value] per 1000 ([value] to [value]) | ||||
Non-serious adverse events [follow-up] | Low risk population | RR [value] ([value] to [value]) | [value] ([value]) | ⊕⊝⊝⊝ very low ⊕⊕⊝⊝ low ⊕⊕⊕⊝ moderate ⊕⊕⊕⊕ high | |
[value] per 1000 | [value] per 1000 ([value] to [value]) | ||||
Medium risk population | |||||
[value] per 1000 | [value] per 1000 ([value] to [value]) | ||||
High risk population | |||||
[value] per 1000 | [value] per 1000 ([value] to [value]) |