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American Journal of Kidney Diseases

Dialysis Modality Survival Comparison: Time to End the Debate, It’s a Tie

  • Bernard G. Jaar
    Correspondence
    Address for Correspondence: Bernard G. Jaar, MD, MPH, 5601 Loch Raven Blvd, Ste 3 N, Baltimore, MD 21239.
    Affiliations
    Division of Nephrology, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD

    Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD

    Welch Center for Prevention, Epidemiology and Clinical Research, Johns Hopkins University, Baltimore, MD

    Nephrology Center of Maryland, Baltimore, MD
    Search for articles by this author
  • Luis F. Gimenez
    Affiliations
    Division of Nephrology, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD

    Nephrology Center of Maryland, Baltimore, MD
    Search for articles by this author
      Related Article, p. 344
      Chronic kidney disease remains a significant public health burden, with more than 678,000 prevalent patients with end-stage renal disease (ESRD) in the United States at the end of 2014.
      • Saran R.
      • Robinson B.
      • Abbott K.C.
      • et al.
      US Renal Data System 2016 annual data report: epidemiology of kidney disease in the United States.
      Regrettably, this number continues to increase by about 21,000 new cases every year, with only 2.6% receiving a preemptive kidney transplant.
      • Saran R.
      • Robinson B.
      • Abbott K.C.
      • et al.
      US Renal Data System 2016 annual data report: epidemiology of kidney disease in the United States.
      The vast majority of these incident patients with ESRD are initiated on hemodialysis (HD) therapy, with <10% on peritoneal dialysis (PD) therapy.
      • Saran R.
      • Robinson B.
      • Abbott K.C.
      • et al.
      US Renal Data System 2016 annual data report: epidemiology of kidney disease in the United States.
      During the past several decades, numerous studies have attempted to compare the risk for death between HD and PD, with conflicting results.
      • Jaar B.G.
      • Coresh J.
      • Plantinga L.C.
      • et al.
      Comparing the risk for death with peritoneal dialysis and hemodialysis in a national cohort of patients with chronic kidney disease.
      • Held P.J.
      • Port F.K.
      • Turenne M.N.
      • Gaylin D.S.
      • Hamburger R.J.
      • Wolfe R.A.
      Continuous ambulatory peritoneal dialysis and hemodialysis: comparison of patient mortality with adjustment for comorbid conditions.
      • Fenton S.S.
      • Schaubel D.E.
      • Desmeules M.
      • et al.
      Hemodialysis versus peritoneal dialysis: a comparison of adjusted mortality rates.
      • Mehrotra R.
      • Chiu Y.W.
      • Kalantar-Zadeh K.
      • Bargman J.
      • Vonesh E.
      Similar outcomes with hemodialysis and peritoneal dialysis in patients with end-stage renal disease.
      • Collins A.J.
      • Hao W.
      • Xia H.
      • et al.
      Mortality risks of peritoneal dialysis and hemodialysis.
      • Vonesh E.
      • Snyder J.J.
      • Foley R.N.
      • Collins A.J.
      The differential impact of risk factors on mortality in hemodialysis and peritoneal dialysis.
      The ideal study design, a randomized controlled trial, has not been possible to date because of low enrollment, in large part driven by patients’ preferences for one dialysis modality or the other after appropriate education.
      • Korevaar J.C.
      • Feith G.W.
      • Dekker F.W.
      • et al.
      Effect of starting with hemodialysis compared with peritoneal dialysis in patients new on dialysis treatment: a randomized controlled trial. NECOSAD Study Group.
      In the end, we are left with the interpretation of observational studies and all their inherent limitations, using either retrospective cohorts of large administrative databases such as the US Renal Data System or smaller more complete prospective cohorts.
      • Jaar B.G.
      • Coresh J.
      • Plantinga L.C.
      • et al.
      Comparing the risk for death with peritoneal dialysis and hemodialysis in a national cohort of patients with chronic kidney disease.
      • Mehrotra R.
      • Chiu Y.W.
      • Kalantar-Zadeh K.
      • Bargman J.
      • Vonesh E.
      Similar outcomes with hemodialysis and peritoneal dialysis in patients with end-stage renal disease.
      • Collins A.J.
      • Hao W.
      • Xia H.
      • et al.
      Mortality risks of peritoneal dialysis and hemodialysis.
      • Vonesh E.
      • Snyder J.J.
      • Foley R.N.
      • Collins A.J.
      The differential impact of risk factors on mortality in hemodialysis and peritoneal dialysis.
      • Termorshuizen F.
      • Korevaar J.C.
      • Dekker F.W.
      • Van Manen J.G.
      • Boeschoten E.W.
      • Krediet R.T.
      Netherlands Cooperative Study on the Adequacy of Dialysis Study Group
      Hemodialysis and peritoneal dialysis: comparison of adjusted mortality rates according to the duration of dialysis: analysis of the Netherlands Cooperative Study on the Adequacy of Dialysis 2.
      Some important limitations of these cohort studies include the use of a noncontemporary cohort, the use of a prevalent population (survival bias), limited information for the presence or severity of comorbid medical conditions (information bias), and short follow-up time. Among these limitations, selection bias may be one of the most significant. As examples, patients with ESRD who are referred late to dialysis therapy and who are sicker are more likely to be initiated on HD therapy with a dialysis catheter, resulting in an initial observed survival advantage for PD as compared to HD.
      • Jaar B.G.
      The Achilles heel of mortality risk by dialysis modality is selection bias.
      In this issue of AJKD, Wong et al
      • Wong B.
      • Ravani P.
      • Oliver M.J.
      • et al.
      Comparison of patient survival between hemodialysis and peritoneal dialysis among patients eligible for both modalities.
      have taken us one step further in the study of survival comparison between HD and PD patients. The authors conducted a retrospective cohort study between January 2004 and December 2013, limited to 7 dialysis centers from the province of Ontario, Canada. These patients not only were all confirmed to have ESRD and to have received outpatient dialysis treatment, but most importantly, also to have undergone a multidisciplinary modality assessment before initiating dialysis therapy. This assessment was structured and included a nephrologist, a predialysis nurse, a PD or acute care nurse, and a social worker who ascertained the patient’s eligibility for HD and PD. These patients were all educated about dialysis modality options and made an informed selection of their chosen dialysis therapy. Of note, patients with a potential follow-up of less than 6 months were excluded to limit the risk for selection bias in favor of acute HD therapy starts, which typically are associated with poor prognosis for survival.
      The authors astutely assembled and compared 3 different groups of dialysis patients to demonstrate the effect of selection bias when comparing survival between HD and PD patients. The “traditional cohort,” labeled as such to mimic cohorts used in prior studies, included all patients with ESRD irrespective of their propensity to do PD. The “eligible cohort” included only patients with ESRD who were medically suitable for both HD and PD. The “eligible outpatient cohort” included patients with ESRD who were suitable for both dialysis modalities but started their treatment electively as outpatients. Because of the study design, there is residual confounding; however, in their statistical analyses, the authors accounted for an extensive list of potential confounders, such as demographic variables, socioeconomic status, comorbid medical conditions, predialysis care, inpatient start of dialysis therapy, and commonly available laboratory data (hemoglobin, serum creatinine, and albumin).
      Overall, a third of the population was deemed not eligible to be treated with PD. In the traditional cohort and eligible cohort, HD patients had a worse clinical profile compared with PD patients, but in the eligible outpatient cohort, clinical profiles were similar between the 2 modalities. When assessing survival, the authors reported that only in the traditional cohort (and limited to patients <65 years old), the risk for death was 40% significantly lower in PD patients in the first 3 years of follow-up. In this traditional cohort, there was no survival advantage by dialysis modality in patients 65 years and older. More importantly, in cohorts with less selection bias, the eligible cohort and eligible outpatient cohort, the authors reported no significant difference in survival between HD and PD, but also no change in survival over time between these dialysis modalities.
      As with all observational studies, there are limitations, which the authors openly discussed. One of the limitations worth noting is the issue of generalizability of the results because the studied population was restricted to only 7 outpatient dialysis centers located in the province of Ontario. Notwithstanding this issue, the authors were able to gather and present data from an incident, more contemporary cohort of dialysis patients with comprehensive data collection (providing a wealth of information) who underwent a structured assessment for dialysis modality eligibility at the outset of the study, again limiting selection bias.
      The findings reported by Wong et al are in line with more recent cohort studies from North America assessing the risk for death between in-center HD and PD patients.
      • Mehrotra R.
      • Chiu Y.W.
      • Kalantar-Zadeh K.
      • Bargman J.
      • Vonesh E.
      Similar outcomes with hemodialysis and peritoneal dialysis in patients with end-stage renal disease.
      • Wong B.
      • Ravani P.
      • Oliver M.J.
      • et al.
      Comparison of patient survival between hemodialysis and peritoneal dialysis among patients eligible for both modalities.
      • Quinn R.R.
      • Hux J.E.
      • Oliver M.J.
      • Austin P.C.
      • Tonelli M.
      • Laupacis A.
      Selection bias explains apparent differential mortality between dialysis modalities.
      • Perl J.
      • Wald R.
      • McFarlane P.
      • et al.
      Hemodialysis vascular access modifies the association between dialysis modality and survival.
      These studies have confirmed that when selection bias is better “handled”, the risk for death between HD and PD patients is not different. From this point of view, practicing nephrologists should feel comfortable offering both dialysis modalities to eligible patients with ESRD. Beyond survival, other factors such as quality of life and patient satisfaction with care may also be important factors to consider in this population. For many patients, having quality of life that is better adapted to their usual lifestyle may be central in their dialysis modality decision-making process. A few cross-sectional studies have shown that quality of life may be better in PD patients as compared with HD patients. However, at least one prospective cohort study has shown that the initial quality-of-life benefit observed in PD patients may not persist in all domains at 1 year of follow-up, as compared with HD patients showing more improvement in quality-of-life domains such as physical functioning and general health perception.
      • Ginieri-Coccossis M.
      • Theofilou P.
      • Synodinou C.
      • Tomaras V.
      • Soldatos C.
      Quality of life, mental health and health beliefs in haemodialysis and peritoneal dialysis patients: investigating differences in early and later years of current treatment.
      • Zhang A.-H.
      • Cheng L.-T.
      • Zhu N.
      • Sun L.-H.
      • Wang T.
      Comparison of quality of life and causes of hospitalization between hemodialysis and peritoneal dialysis patients in China.
      • Wu A.W.
      • Fink N.E.
      • Marsh-Manzi J.V.
      • et al.
      Changes in quality of life during hemodialysis and peritoneal dialysis treatment: generic and disease specific measures.
      Patient satisfaction with care received may also be a significant factor considered by many. PD patients are typically more likely to give excellent ratings of overall care received and for each aspect of that care compared with patients receiving HD.
      • Rubin H.R.
      • Fink N.E.
      • Plantinga L.C.
      • Sadler J.H.
      • Kliger A.S.
      • Powe N.R.
      Patient ratings of dialysis care with peritoneal dialysis vs hemodialysis.
      As cost of care continues to increase, providers need to be aware of this important shared problem and provide access to treatment that may be more cost-effective without compromising patients’ health and outcomes such as survival and quality of life. Many studies have now confirmed that PD as a dialysis modality is associated overall with lower cost of care compared to HD.
      • Saran R.
      • Robinson B.
      • Abbott K.C.
      • et al.
      US Renal Data System 2016 annual data report: epidemiology of kidney disease in the United States.
      • Karopadi A.N.
      • Mason G.
      • Rettore E.
      • Ronco C.
      Cost of peritoneal dialysis and hemodialysis across the world.
      • Berger A.
      • Edelsberg J.
      • Inglese G.W.
      • Bhattacharyya S.K.
      • Oster G.
      Cost comparison of peritoneal dialysis versus hemodialysis in end-stage renal disease.
      In the United States, as of 2014, the cost of PD per patient per year was about $14,000 less compared to HD.
      • Saran R.
      • Robinson B.
      • Abbott K.C.
      • et al.
      US Renal Data System 2016 annual data report: epidemiology of kidney disease in the United States.
      Based on the best available and contemporary evidence, there is no observed difference in the risk for death between HD and PD. This report by Wong et al is one more study that elegantly supports this conclusion when analyses account for patients’ eligibility for either dialysis modality, thus limiting selection bias.
      • Wong B.
      • Ravani P.
      • Oliver M.J.
      • et al.
      Comparison of patient survival between hemodialysis and peritoneal dialysis among patients eligible for both modalities.
      Although recent policy changes have helped improve the use of home therapies, including home HD and PD, these 2 modalities remain underused and further steps are still critically needed to continue to expand their use.
      • Lin E.
      • Cheng X.S.
      • Chin K.K.
      • et al.
      Home dialysis in the prospective payment system era.
      For example, we need to continue to improve our renal fellows’ education on home dialysis therapies, with longitudinal exposure to these modalities (home HD and PD) on an outpatient basis as part of their outpatient nephrology clinical experience. We also need to further refine and improve on our patients’ dialysis education programs, making sure that every patient with ESRD is informed about his or her renal replacement therapy options (including kidney transplantation and types of dialysis modality) and also to incorporate a discussion about palliative care when appropriate.
      Ultimately, we need to keep in mind that for patients with ESRD who choose renal replacement therapy over palliative care, HD and PD have specific trade-offs, but also are interchangeable and should be seen as a bridge to kidney transplantation, which remains the gold standard for ESRD therapy in eligible patients.

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