“…Of 721 RAS cases, around 56% ( n = 404) were females ( Table 1 ). Eight studies ( 28 – 30 , 32 , 34 , 35 , 39 , 40 ) included patients with minor RAS, two studies ( 18 , 33 ) included patients with minor, major, and herpetiform RAS, and one study ( 12 ) included patients with minor and major RAS, while three studies ( 11 , 13 , 14 ) did not mention the type of RAS. All the included studies assessed the serum levels of vitamin D, seven of which used ELISA (enzyme-linked immunosorbent assay) ( 29 , 30 , 32 – 35 , 40 ), while four studies ( 11 , 18 , 28 , 39 ) used ECLIA (electro-chemiluminescence binding assay).…”