“…A total of 20 studies were included in the qualitative and quantitative synthesis ( Fig. 1 , Table 1 ) [ 2 , [14] , [15] , [16] , [17] , [18] , [19] , [20] , [21] , [22] , [23] , [24] , [25] , [26] , [27] , [28] , [29] , [30] , [31] , [32] ]. One study which we included described an OR value.…”