“…Among the 32 included studies, 6 studies belonged to the group A [1, 2, 9–11, 38], 9 studies belonged to the group B [23–25, 27–29, 31–33], and 17 studies belonged to the group C [13–22, 36, 37, 39–43]. As for the effect size, RDW was reported as a continuous variable (per 1% increase) in 16 studies [1, 9–11, 16, 17, 21–23, 29, 31, 32, 36, 37, 40, 43], as a binary variable in 8 studies [14, 16, 18, 19, 26, 33, 36, 40], and as a categorical variable in 8 studies [2, 13, 17, 22, 25, 27, 29, 42]. The AUC of RDW for mortality prediction was reported in 25 studies.…”