This meta-analysis includes seven studies in which the use of EPO was allowed [19, 22, 23, 26, 30, 33, 35], but erythropoietin was not considered as a covariate because: (1) the percentage of patients who received erythropoietin was low (3 %) (data not shown); (2) some studies did not provide this information or is not detailed; and (3) in most cases, the anemia occurred before treatment with erythropoietin was administered. Here, EPO is linked to anemia.