This problem is addressed in PRISMA 2009, PRISMA 2020, AMSTAR-2, ROBIS and MECIR. Sometimes changes to the primary outcome in a systematic review are made after knowledge of individual trials. The primary outcome for the systematic review should be prespecified and any amendments from the protocol to the main outcome of interest should be fully documented and justifed in the final report.
Articles that support this problem:
Selective reporting of outcomes in randomised controlled trials in systematic reviews of cystic fibrosis
2013 : Bmj open
Bias due to selective inclusion and reporting of outcomes and analyses in systematic reviews of randomised trials of healthcare interventions
2014 : The cochrane library
Outcome reporting bias in Cochrane systematic reviews: a cross-sectional analysis
2020 : Bmj open
Inadvertent P-hacking among trials and systematic reviews of the effect of progestogens in pregnancy? A systematic review and meta-analysis
2017 : Bjog: an international journal of obstetrics & gynaecology
Generalizability of findings from systematic reviews and meta-analyses in the Leading General Medical Journals
2020 : Journal of rehabilitation medicine
Many scenarios exist for selective inclusion and reporting of results in randomized trials and systematic reviews
2013 : Journal of clinical epidemiology
Multivariate meta-analysis helps examine the impact of outcome reporting bias in Cochrane rheumatoid arthritis reviews
2015 : Journal of clinical epidemiology
Methods to select results to include in meta-analyses deserve more consideration in systematic reviews
2015 : Journal of clinical epidemiology
Survey of new 2007 and 2011 Cochrane reviews found 37% of prespecified outcomes not reported
2015 : Journal of clinical epidemiology
Attention should be given to multiplicity issues in systematic reviews
2008 : Journal of clinical epidemiology
Dealing with effect size multiplicity in systematic reviews and meta‐analyses
2018 : Research synthesis methods
A third of systematic reviews changed or did not specify the primary outcome: a PROSPERO register study
2016 : Journal of clinical epidemiology
A systematic survey showed important limitations in the methods for assessing drug safety among systematic reviews
2020 : Journal of clinical epidemiology
The impact of outcome reporting bias in randomised controlled trials on a cohort of systematic reviews
2010 : Bmj
Multiplicity of data in trial reports and the reliability of meta-analyses: empirical study
2011 : Bmj
Outcomes in Cochrane systematic reviews related to wound care: An investigation into prespecification
2017 : Wound repair & regeneration
Identification and impact of outcome selection bias in meta‐analysis
2005 : Statistics in medicine
Registration of systematic reviews in PROSPERO: 30,000 records and counting
2018 : Systematic reviews
A meta-epidemiological study of subgroup analyses in cochrane systematic reviews of atrial fibrillation
2019 : Systematic reviews
Association between unreported outcomes and effect size estimates in Cochrane meta-analyses
2007 : Jama
Exploring treatment by covariate interactions using subgroup analysis and meta-regression in cochrane reviews: a review of recent practice
2015 : Plos one
Bias due to changes in specified outcomes during the systematic review process
2010 : Plos one
Outcomes in Cochrane systematic reviews addressing four common eye conditions: an evaluation of completeness and comparability
2014 : Plos one
Strong heterogeneity of outcome reporting in systematic reviews
2016 : Journal of clinical epidemiology
Inclusion criteria for outcomes of studies not clearly reported in Cochrane systematic reviews
2017 : Journal of clinical epidemiology
Discrepancies in outcome reporting exist between protocols and published oral health Cochrane systematic reviews
2015 : Plos one
Statistical multiplicity in systematic reviews of anaesthesia interventions: a quantification and comparison between Cochrane and non-Cochrane reviews
2011 : Plos one
Age-treatment subgroup analyses in Cochrane intervention reviews: a meta-epidemiological study
2019 : Bmc medicine
Clinical heterogeneity was a common problem in Cochrane reviews of physiotherapy and occupational therapy
2006 : Journal of clinical epidemiology
A descriptive analysis of child-relevant systematic reviews in the Cochrane Database of Systematic Reviews
2010 : Bmc pediatrics
Investigation of bias in meta-analyses due to selective inclusion of trial effect estimates: empirical study
2016 : Bmj open
The fate of urological systematic reviews registered in PROSPERO
2019 : World journal of urology
Reporting bias in the literature on the associations of health-related behaviors and statins with cardiovascular disease and all-cause mortality
2018 : Plos biology
Epidemiology and Reporting Characteristics of Systematic Reviews of Biomedical Research: A Cross-Sectional Study
2016 : Plos medicine
Missing Data in Systematic Reviews and Meta-Analysis
2022 : Pediatric critical care medicine
Substantial heterogeneity found in reporting mortality in Cochrane systematic reviews and Core Outcome Sets in COMET database
2022 : Journal of clinical epidemiology