Table 1.

Characteristics of studies included in this meta-analysis

Author	Year	Country	Ethnicity	Language	Case	Control	Research method	Score
Buraczynska [16]	2016	Poland	Caucasian	English	368	722	RFLP-PCR	9
Balistreri [17]	2014	Italy	Caucasian	English	48	319	RFLP-PCR	9
Khaghanzadeh [15]	2020	Iran	Asian	English	11	89	SSP-PCR	8
Balistreri* [17]	2014	Italy	Caucasian	English	112	255	RFLP-PCR	9
Buraczynska* [16]	2016	Poland	Caucasian	English	342	748	RFLP-PCR	9
Buraczynska* [18]	2009	Poland	Caucasian	English	352	512	RFLP-PCR	9
Singh* [19]	2014	India	Asian	English	128	250	RFLP-PCR	9
Zaharieva * [20]	2017	Bulgaria	Caucasian	English	10	75	PCR	8
Balistreri** [17]	2014	Italy	Caucasian	English	74	293	RFLP-PCR	9
Buraczynska**[16]	2016	Poland	Caucasian	English	302	788	RFLP-PCR	9
Zaharieva** [20]	2017	Bulgaria	Caucasian	English	87	18	PCR	8

*Diabetic retinopathy; **diabetic neuropathy; without*diabetic nephropathy. PCR: Polymerase chain reaction; SSP-PCR: Polymerase chain reaction sequence specific primers; PCR–RFLP: PCR-restriction fragment length polymorphism