Table 3. The main characteristics of the systematic review and meta-analysis included in the review.

SLE: systemic lupus erythematosus; OR: odds ratio; CI: confidence interval

Author	Year	Type of study	Databases reviewed	Number of studies included	Total participants	Inclusion and exclusion criteria	Outcomes and key points	Funding
Lee et al. [23]	2018	Meta-analysis	Medline, Embase, Cochrane	20	1,333 patients and 1,048 controls	Inclusion criteria: case-control, cross-sectional, or cohort studies with data on serum/plasma leptin levels in case and control groups. No language and race restrictions. Exclusion criteria: overlapping or insufficient data, reviews, and case reports	Leptin levels were elevated in SLE patients regardless of ethnicity, data type, sample size, and matched variables. The study proposed that leptin may have an important role in the pathogenesis of SLE, but the exact mechanism is not clear	No external funding
Yuan et al. [4]	2020	Systematic review and meta-analysis	PubMed, Embase, Cochrane, China National Knowledge Infrastructure, China WanFang, China Weipu	34	1,744 patients and 1,411 controls	Inclusion criteria: cohort, case-control, and cross-sectional studies with data on the serum/plasma leptin levels, leptin receptor levels, and relevant gene polymorphism in case and control groups, studies with predefined SLE criteria and measurement methods, studies with OR estimates with 95% CI and p-values. Exclusion criteria: case reports, editorials, letters, comments, review articles, meta-analysis, and non-human subjects	Leptin levels were higher in SLE patients regardless of source, sample size, or assay method. In terms of ethnicity, leptin levels were elevated in Asian, African, North American, and European groups. SLE patients showed a decreased trend of leptin receptor levels	Received external funding