Explaining International Trends in Mortality on Hemodialysis Through Changes in Hemodialysis Practices in the Dialysis Outcomes and Practice Patterns Study (DOPPS)

Abstract

Rationale & objective: Case-mix adjusted hemodialysis mortality has decreased since 1998. Many factors that influence mortality may have contributed to this trend, and these associations may differ by continental region. We studied changes in hemodialysis facility practices over time and their potential role in mediating changes in patient survival.

Study design: Observational prospective cohort study.

Setting & participants: Adult hemodialysis patients treated in 500 hemodialysis facilities participating in the Dialysis Outcomes and Practice Patterns Study (DOPPS) between 1999 and 2015 in the United States, Japan, and 4 European countries: Germany, Italy, Spain, and the United Kingdom.

Predictors: Four practice measures at each facility: the percentages of patients with Kt/V≥1.2, interdialytic weight gain [IDWG]<5.7%, phosphorus<6mg/dL, and using arteriovenous fistulas (AVFs).

Outcome: Patient survival.

Analytical approach: Mediation analyses, adjusted for case mix, were conducted using 3-year study phase as the exposure and facility practice measures as potential mediators.

Results: In Europe, we observed a 13% improvement in overall case-mix adjusted survival per decade. Trends in facility practice measures, especially Kt/V and phosphorus, explained 10% improvement in case-mix survival per decade, representing 77% (10% explained of 13% improvement) of the observed improvement. In Japan, 73% of the observed 12%/decade improvement in case-mix adjusted survival could be attributed to facility practices, especially Kt/V and IDWG. In the United States, 56% of the observed 47%/decade improvement in case-mix adjusted survival could be attributed to facility practices, especially AVF use and phosphorus control.

Limitations: Unmeasured changes in the characteristics of the patient population over this period may confound the observed associations.

Conclusions: The improvements in adjusted hemodialysis patient survival in Europe, Japan, and the United States from 1999 to 2015 can be largely explained by improvements in specific facility practices. Future changes in patient survival may be responsive to further evolution in the implementation of common clinical practices.

Plain-language summary: Case-mix adjusted survival of patients treated with hemodialysis has improved over the last 2 decades in the United States, Japan, and Europe. Some of this improvement can be explained by region-specific changes in 4 dialysis practices, namely increases in the proportions of patients achieving (1) Kt/V≥1.2, (2) serum phosphorus levels<6mg/dL, (3) interdialytic weight gain<5.7% of body weight, and/or (4) use of arteriovenous fistulas as vascular access, with the magnitude varying according to region-specific trends in these practices. These findings suggest that further improvement in these practice measures may be attended by further reductions in mortality among patients treated with maintenance hemodialysis.

Keywords: Clinical practice; DOPPS; epidemiology; hemodialysis; mediation analyses; mortality trends; patient survival; practice trends.