Since the 1990s, the risk of dying from infections after kidney transplantation has dropped by half, according to a recent analysis. The analysis, which appears in an upcoming issue of the Clinical Journal of the American Society of Nephrology, also found that common bacterial infections remain the most frequent cause of infection-related death among transplant recipients.

The study was carried out by researchers from the University of Eastern Finland, the University of Helsinki, Kuopio University Hospital, and Helsinki University Hospital.

The risk of infection is something that all nephrologists think of when a patient is considered for transplantation. Indeed, infections are the most common non-cardiovascular causes of death after kidney transplantation, likely due to patients’ need for immunosuppressive medications to prevent rejection. No recent data about the infectious causes of death after kidney transplantation exist, however.

To provide an estimate on infection-related mortality among kidney transplant recipients in a modern developed country, a team led by Ilkka Helanterä, MD, PhD (Helsinki University Hospital) and Susanna Kinnunen, MD (University of Eastern Finland and Kuopio University Hospital) examined data on all adult recipients of a first kidney transplantation between 1990 and 2012 in Finland. Infectious causes of death were analyzed, and the mortality rates for infections were compared between two eras (1990-1999 and 2000-2012). The data were obtained from the Finnish Registry for Kidney Diseases.

Among the 3,249 adult recipients of a first kidney transplant in the analysis, 953 patients (29%) died during follow-up, with 204 infection-related deaths. The mortality rate due to infections was lower in patients in the more recent era than in patients in the 1990s (4.6 vs 9.1 per 1,000 person-years. A person-year is the number of years of follow-up multiplied by the number of people in the analysis.) Common bacterial infections were the most frequent cause of infection-related mortality, whereas opportunistic viral, fungal, or unconventional bacterial infections rarely caused deaths after kidney transplantation. Older recipient age, higher plasma creatinine concentration at the end of the first post-transplant year, diabetes as a cause of kidney failure, longer pre-transplant dialysis duration, acute rejection, low albumin level, and earlier era of transplantation were associated with higher risks of infectious death.

According to the researchers, “The study shows that the risk of infectious mortality in patients with a kidney transplant is much lower than previously thought, and that the risk has dropped by half in the 2000s in our cohort despite transplanting older and sicker patients and using more powerful immunosuppression.” They note that the discovery that the infections that cause death in transplant recipients are very similar to the infections that cause mortality in the general population is contrary to current thinking among experts. “In addition, surprisingly low number of infectious deaths were recorded during the first year after transplantation, and most of the infectious deaths occurred late, several years after transplantation.”