Association of 25-Hydroxyvitamin D Levels with BK Viremia and Nephropathy in Kidney Transplant Recipients

Background: In kidney transplant recipients, BK virus reactivation and subsequent viremia (BKV) and nephropathy (BKN) are significant causes of morbidity and mortality. Limited treatment options make these complications particularly detrimental. Vitamin D supports immune function, yet low 25-hydroxyvitamin D [25(OH)D] levels are common in kidney transplant recipients. The association between 25(OH)D and BKV and BKN in kidney transplant recipients remains undefined. Methods: The relationship between serum 25(OH)D level, measured 61 days to 2 years post-transplant, and BKV and BKN was examined in 3308 kidney transplant recipients. Recipients received kidney transplants from 2010 to 2019. Only recipients with 25(OH)D level measured before BKV were included. Results: Out of 3308 recipients, 399 (12%) were vitamin D deficient [25(OH)D <20 ng/mL], and 916 (27.7%) were insufficient [25(OH)D 20-29 ng/mL]. 184 recipients had BKV, and 44 recipients had BKN. The incidence rate for BKV/100 person-years was 2.88 in the 25(OH)D sufficient group, 2.22 in the insufficient group, and 2.37 in the deficient group. With reference to sufficient 25(OH)D, there was no significant association for BKV after adjustment for multiple baseline characteristics. Similarly, the incidence rate/100 person-years for BKN was 0.30 in the 25(OH)D sufficient group, 0.75 in the insufficient group, and 1.28 in the deficient group. After adjustment for multiple baseline characteristics, with reference to sufficient 25(OH)D, deficiency (aHR: 3.92; 95% CI: 1.66-9.23) and insufficiency (aHR: 2.22; 95% CI: 1.11-4.45) were significantly associated with increased risk for BKN (Figure 1). Conclusion: Low serum 25(OH)D is associated with increased risk of BKN but not BKV. Further studies are needed to explore the effects of vitamin D supplements to mitigate complications associated with BKN.Figure 1. Incidence of BKN decreased with increasing 25(OH)D.