The Association between Vitamin D and Rejection in Adult Renal Transplant Recipients: A Meta-Analysis

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The problem has been discussed a lot, but the results remain controversial. Since no consensus had been reached yet for whether vitamin D insufficient is a major contributor for rejection in renal transplant patients, we performed a meta-analysis of the association between them. Pub Med, Medline, web of science, Ovid and Springer databases were searched for observational studies linked with vitamin D and rejection in adult renal transplant recipients. A meta-analysis was conducted by pooling data from relevant cohort and case control studies. The Q statistic and I2 were used to measure heterogeneity. Subgroup analysis and meta-regression were conducted to detect the source of heterogeneity. When significant heterogeneity was observed statistically, a random-effect model can be used to estimate the odds ratio. And sensitivity analysis was conducted to make sure whether the results were stable. The analysis consisted of seven studies including five cohort studies and two case control studies, with a total of 2731 participants. These studies contained different vitamin D doses with a varying degree of intervention duration. Pooled odds ratio was 1.07, 95% confidence interval: [0.50-2.28], with significant heterogeneity among these studies (I2=82%, P<0.01). Vitamin D has no association with rejection in adult renal transplant recipients. There is a necessity that future investigations are encouraged to reveal the underlying mechanisms and the risk factors for rejection.

Chronic Kidney Diseases (CKD) is highly prevalent in the general population, which have become a worldwide epidemic with an occurrence rate of approximately 5%-15%. When the CKD is developing to End-Stage Renal Disease (ESRD), kidney transplantation is a preferred treatment for the increasing number of patients. Renal transplant recipients usually have low vitamin D levels, especially in the early post-transplantation period. Vitamin D is an important hormone which closely correlated with many immune disorders. It not only maintains the basic metabolism of calcium and phosphorus, but also affects immune functions of the body. More and more people have realized that vitamin D is one of the largest modifiable risk factors for health.

Since the kidney is an active organ of vitamin D, it is also increasingly appreciated that there may be an association between vitamin D and allograft outcomes in renal transplant recipients. Some retrospective cohort studies stated that vitamin D can improve the prognosis of graft, reduce graft loss and prevent rejection by inhibiting allograft rejection.