Thrombotic microangiopathy in United States long-term dialysis patients

Background. The incidence, risk factors, recurrence rates and prognosis of thrombotic microangiopathy (TMA) among long-term dialysis patients in the United States have not been previously described in a national population. Methods. 272 024 Medicare primary patients in the United States Renal Data System (USRDS) initiated on end-stage renal disease (ESRD) therapy between 1 April 1995 and 31 December 1999 with Medicare as primary payer were analysed in a retrospective cohort study of USRDS of TMA. Cox regression was used to calculate adjusted hazard ratios (AHR) for risk of TMA and risk of death after TMA. Results. The incidence of TMA in the first year of dialysis was 0.5% overall. Among patients with renal failure due to haemolytic uraemic syndrome (HUS), the incidence of TMA was highest in the first year of dialysis (HUS, 11.3% first year, 4.5% per year thereafter), while among patients without HUS the incidence of TMA was much lower and more constant over time (0.3% per year). In Cox regression analysis, independent risk factors for TMA were renal failure due to HUS (adjusted hazard ratio (AHR) 179, 95% CI 95-338), paediatric age (≤18 years vs older, AHR 2.59, 95% CI 1.48-4.55), female gender (AHR 1.99, 95% CI 1.43-2.78), and systemic lupus erythematosus (SLE, AHR 3.66, 95% CI 1.49-8.51). One-year survival after TMA was poor at 58% (AHR for mortality 2.04, 95% CI 1.23-3.38). Conclusions. TMA is an uncommon cause of hospitalization after dialysis, but does recur in patients with HUS at a substantial rate. Younger age and SLE were risk factors for new onset TMA, which was associated with poor survival. Vigilant monitoring of select patients with HUS-related ESRD and higher-risk patients with SLE is warranted in the dialysis population.