Background: Vitamin D (VitD) de ciency is associated with several diseases such as multiple sclerosis, rheumatoid arthritis, respiratory infection, and so forth. In the eld of transplantation (kidney transplantation), some studies reported that patients with VitD de ciency are of increased risk of acute rejection, but other studies did not show such a risk. On the other hand, since VitD is a modulatory factor and can reduce the in ammatory response, understanding the exact role of it in transplantation may contribute to tolerance condition in these patients.Methods: The electronic databases, including PubMed, Scopus, Embase, ProQuest, Web of Science, and Google Scholar, were searched for eligible studies. In general, 14 studies with a total of 4,770 patients were included in this meta-analysis. Regarding the methodological heterogeneity, we selected a random-effects combination model. Moreover, OR was chosen as an effect size for this study.Results: After the combination of 14 studies, we showed that patients in the VitD-de cient group had an 82% increased risk of acute rejection compared with patients in the VitD-su cient group, and this effect was signi cant (OR 1.82; 95% con dence interval [CI] [1.29, 2.56]; I 2 = 52.3%). This result was signi cant, and, regarding the narrow CI, it can be a conclusive result. Study quality and gender variables were the main sources of inconsistent results in the primary studies. Moreover, using meta-regression, we showed that VitD de ciency (independent from the estimated glomerular ltration rate (eGFR) of patients) increased the risk of acute rejection.
Conclusion:The normal VitD status of patients a few days before and after transplantation can reduce the risk of acute rejection, as it has de nite modulatory effects on immune cells.
