Association of Posttransplant Circulating 25-Hydroxyvitamin D and Late-Onset Infections Among Kidney Transplant Recipients: The Wisconsin Allograft Recipient Database (WisARD).

introductionLate-onset infection occurring more than 6 months after transplantation is a major threat to the long-term survival of kidney transplant recipients (KTRs). Accumulating evidence indicates a potential role for vitamin D in host resistance to infections. While vitamin D inadequacy is common among KTRs, the association of posttransplant circulating 25-hydroxyvitamin D [25(OH)D] and late-onset infection remains uncertain.

methodsWe analyzed data from adult kidney-only transplant recipients at our center from 2005 to 2020 who had at least one valid posttransplant circulating 25(OH)D measurement from 5 to 13 months posttransplant. Survival analyses were conducted using marginal proportional rates models with late-onset infection within 1 year following the 25(OH)D measurement as the event of interest. Additional analyses used time-varying 25(OH)D measurements.

resultsOf 2207 KTRs included, 642 recipients had a total of 1448 late-onset infection episodes. Each 5 ng/mL lower serum 25(OH)D was associated with a 5% higher risk of late-onset infection (adjusted rate ratio [aRR] = 1.05; 95% confidence interval [CI]: 1.03, 1.07; p < 0.01). Vitamin D deficiency (≤ 20 ng/mL) was associated with a 1.22-fold higher incidence of late-onset infection (aRR = 1.22; 95% CI: 1.03-1.43; p = 0.02) compared with vitamin D sufficiency (≥30 ng/mL). The association was strongest for urinary tract infection among male recipients (aRR = 2.20; 95% CI: 1.57-3.08; p < 0.01).

conclusionVitamin D deficiency is significantly associated with a higher incidence of late-onset infection among KTRs, especially urinary tract infections in male recipients. Further research, including clinical trials, is needed to determine the causal relationship.