The association between vitamin D and acute rejection in human kidney transplantation: A systematic review and meta-analysis study

Background: Vitamin D (VitD) deficiency is associated with several diseases such as multiple sclerosis, rheumatoid arthritis, respiratory infection, and so forth. In the field of transplantation (kidney transplantation), some studies reported that patients with VitD deficiency are of increased chance of acute rejection, but other studies did not show such a chance. On the other hand, since VitD is a modulatory factor and can reduce the inflammatory 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 4770 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-deficient group had an 82% increased chance of acute rejection compared with patients in the VitD-sufficient group, and this effect was significant (OR 1.82; 95% confidence interval [CI] [1.29, 2.56]; I2 = 52.3%). This result was significant, 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 deficiency (independent from the estimated glomerular filtration rate (eGFR) of patients) increased the chance of acute rejection. Conclusion: The normal VitD status of patients a few days before and after transplantation can reduce the chance of acute rejection.