Vitamin D deficiency among outpatients and hospitalized patients with diabetic foot ulcers: A systematic review and meta-analysis

Table 3 Newcastle Ottawa scale risk of bias of the included studies

Ref.	Country	Selection bias	Comparability bias	Outcome	Total score
Afarideh et al[18], 2016	Iran	4	2	2	8
Çağlar et al[19], 2018	Turkey	4	2	2	8
Dai et al[20], 2020	China	4	2	2	8
Danny Darlington et al[21], 2019		4	1	2	7
Feldkamp et al[22], 2018	India	4	2	2	8
Gupta et al[23], 2016	Germany	4	2	2	8
Tang et al[24], 2021	India	4	2	2	8
Tiwari et al[25], 2014	China	4	1	2	7
Todorova et al[26], 2020	India	4	2	2	8
Tsitsou et al[27], 2021	Bulgaria	4	1	2	7
Wang et al[28], 2022	Greece	4	2	2	8
Xiao et al[29], 2020	China	4	1	2	7