Table 1.

Main characteristics of the studies included in this meta-analysis

References	Study location	Study design	Method of RBP4 measurement	Diagnostic methods of NAFLD	Quality Score	Additional information
Seo et al. [14]	Korea	Cross-sectional	ELISA	Ultrasound	3
Chen et al. [15]	China	Cross-sectional	ELISA	Ultrasound	3
Milner et al. [16]	Australia	Cross-sectional	ELISA	Liver biopsy	7
Suh et al. [17]	Korea	Cross-sectional	ELISA	Ultrasound	4
Schina et al. [18]	Greece	Cross-sectional	ELISA	Liver biopsy	4
Polyzos et al. [19]	Greece	Cross-sectional	ELISA	Liver biopsy	5	A second control group of 24 lean subjects was not included in the meta-analysis.
Auguet et al. [23]	Spain	Cross-sectional	ELISA	Liver biopsy	6	Patients and controls were morbidly obese women who underwent bariatric surgery.
Koh et al. [24]	Korea	Cross-sectional	ELISA	Ultrasound	5	NAFLD cases and controls were all type 2 diabetic patients.
Wu et al. [25]	China	Cross-sectional	Radioimmunoa- ssay	Ultrasound	3	NAFLD cases and controls were all type 2 diabetic patients.
Cengiz et al. [26]	Turkey	Cross-sectional	ELISA	Ultrasound and liver biopsy	3	34 of 76 NAFLD underwent a liver biopsy.
Kashyap et al. [27]	USA	Cross-sectional	ELISA	Liver biopsy	6	Patients and controls were subjected to bariatric surgery
Alkhouri et al. [28]	USA	Cross-sectional	ELISA	Liver biopsy	4

RBP4 retinol binding protein 4, NAFLD nonalcoholic fatty liver disease