This problem is addressed by the SWIM guideline. Unduly highlighting or favouring certain studies above others or presenting unweighted summary statistics are ways in which the narrative synthesis in a systematic review fails to uphold methodological rigour.
Articles that support this problem:
Reporting quality of systematic reviews of interventions aimed at improving vaccination coverage: compliance with PRISMA guidelines
2019 : Human vaccines & immunotherapeutics
Frequent inappropriate use of unweighted summary statistics in systematic reviews of pathogen genotypes or genogroups
2020 : Journal of clinical epidemiology
Reasons or excuses for avoiding meta-analysis in forest plots
2008 : Bmj
The methodological quality of systematic reviews of animal studies in dentistry
2012 : The veterinary journal
Lack of transparency in reporting narrative synthesis of quantitative data: a methodological assessment of systematic reviews
2019 : Journal of clinical epidemiology
Clinical heterogeneity was a common problem in Cochrane reviews of physiotherapy and occupational therapy
2006 : Journal of clinical epidemiology
Quality of Cochrane reviews: Quality of Cochrane reviews is better than that of non-Cochrane reviews
2002 : Bmj: british medical journal
Methodological concerns about a systematic review and meta-analysis of maternal active smoking during pregnancy and low birth weight.
2019 : Nicotine and tobacco research
Characteristics and quality of systematic reviews of acupuncture, herbal medicines, and homeopathy
2003 : Complementary medicine research
Characteristics and quality of systematic reviews and meta-analyses of observational nutritional epidemiology: a cross-sectional study
2021 : American journal of clinical nutrition
Reliability of the evidence to guide decision-making in foot ulcer prevention in diabetes: an overview of systematic reviews
2022 : Bmc medical research methodology