Transfers to Hemodialysis Among US Patients Initiating Renal Replacement Therapy With Peritoneal Dialysis

Abstract

Rationale & objective: Identifying patients who are likely to transfer from peritoneal dialysis (PD) to hemodialysis (HD) before transition could improve their subsequent care. This study developed a prediction tool for transition from PD to HD.

Study design: Retrospective cohort study.

Setting & participants: Adults initiating PD between January 2008 and December 2011, followed up through June 2015, for whom data were available in the US Renal Data System (USRDS).

Predictors: Clinical characteristics at PD initiation and peritonitis claims.

Outcomes: Transfer to HD, with the competing outcomes of death and kidney transplantation.

Analytical approach: Outcomes were ascertained from USRDS treatment history files. Subdistribution hazards (competing-risk) models were fit using clinical characteristics at PD initiation. A nomogram was developed to classify patient risk at 1, 2, 3, and 4 years. These data were used to generate quartiles of HD transfer risk; this quartile score was incorporated into a cause-specific hazards model that additionally included a time-dependent variable for peritonitis.

Results: 29,573 incident PD patients were followed up for a median of 21.6 (interquartile range, 9.0-42.3) months, during which 41.2% transferred to HD, 25.9% died, 17.1% underwent kidney transplantation, and the rest were followed up to the study end in June 2015. Claims for peritonitis were present in 11,733 (40.2%) patients. The proportion of patients still receiving PD decreased to <50% at 22.6 months and 14.2% at 5 years. Peritonitis was associated with a higher rate of HD transfer (HR, 1.82; 95% CI, 1.76-1.89; P < 0.001), as were higher quartile scores of HD transfer risk (HRs of 1.31 [95% CI, 1.25-1.37), 1.51 [95% CI, 1.45-1.58], and 1.78 [95% CI, 1.71-1.86] for quartiles 2, 3, and 4 compared to quartile 1 [P < 0.001 for all]).

Limitations: Observational data, reliant on the Medical Evidence Report and Medicare claims.

Conclusions: A large majority of the patients who initiated renal replacement therapy with PD discontinued this modality within 5 years. Transfer to HD was the most common outcome. Patient characteristics and comorbid diseases influenced the probability of HD transfer, death, and transplantation, as did episodes of peritonitis.

Keywords: HD transfer; Peritoneal dialysis (PD); competing risks; dialysis modality; hemodialysis (HD); modality switch; nomogram; prediction; prediction tool; prognosis; renal replacement therapy (RRT).

Figure 1.

Flowchart of patients included in the study. Hemodialysis (HD), peritoneal dialysis (PD), glomerular filtration rate (GFR).

Figure 2.

Hemodialysis transfer, kidney transplantation, and death over time, for all incident PD patients. The prevalence of each outcome is shown as the vertical height of the appropriate area at each time point on the horizontal axis.

Figure 3.

Interactions of the subdistribution hazard ratios for HD transfer with patient age. The dashed line shows the sub-distribution hazard ratios for employment versus unemployment, which increases with increasing age. The solid and dotted lines show that the sub-distribution hazard ratios for primary diabetic nephropathy or hypertensive nephropathy versus other causes of kidney failure decrease with increasing age.

Figure 4.

Competing risks nomogram. To calculate points for an individual patient, the patient’s value for each characteristic should be traced upwards to the ‘Points’ axis. For example, a BMI of 40 kg/m2 would receive 50 points. The last three axes (AGE_if_DM, AGE_if_HTN, and AGE_if_employed) represent interaction variables. For patients who meet the conditions specified (diabetic nephropathy, hypertensive nephropathy, employment), points are assessed based on age. For patients who do not meet these conditions (e.g. non-diabetic, not hypertensive nephropathy, unemployed), points are assigned based on the zero-point of the axis. Total score is the sum of points from each patient axis, which is used to draw a vertical line in the lower pane of the nomogram. Predicted cumulative incidences of HD transfer at 12, 24, 36, and 48 months are read from where this vertical line intersects the axes in the lower pane.

Figure 5.

The dotted, dashed, solid black and grey lines represent the cumulative incidences of HD transfer over time among the four risk quartiles assigned in the subdistribution hazards model. Quartile 1 (Q1) has the lowest risk for HD transfer.