The Hopkins findings, to be published in the journal Annals of Internal Medicine online Aug. 1, are from one of the first comprehensive, large-scale, follow-up comparison studies in the debate about which kind of dialysis is better.
Currently, more than 400,000 Americans require one of the two kinds of dialysis to remove waste products and excess water from the blood because their failing kidneys have less than 15 percent of their normal function remaining. On average, a healthy kidney filters approximately 200 quarts of blood per day. By 2030, the number of Americans needing dialysis is expected to jump to 2 million, due in part to rising rates of diabetes, the leading cause of kidney failure.
"Lifelong dialysis is often the only option when a patient's kidneys fail because there are not enough kidneys available for transplantation," says the study's primary author, kidney specialist Bernard G. Jaar, M.D., M.P.H., an assistant professor at the Welch Center for Prevention, Epidemiology and Clinical Research at The Johns Hopkins University School of Medicine. More than 55,000 people are on the national waiting list for a kidney, he says.
"Until now, people with kidney disease have picked the kind of dialysis that best suits their lifestyle, sometimes switching from one method to the other, but we have always wondered if one of the two methods helped people live longer," Jaar adds.
To find out, the study, called the Choices for Healthy Outcomes in Caring for ESRD, or CHOICE for short, followed 1,041 newly diagnosed patients from 81 dialysis clinics across the United States and monitored their health, mainly through reviews of patient charts and medical records, for eight years while they underwent dialysis treatment. The study participants, men and women between 18 and 96 years old, chose the method of dialysis: 274 selected peritoneal dialysis and 767 selected hemodialysis.
In peritoneal dialysis, the membrane lining of the body cavity is used as a substitute filter to do the work of the kidneys. A tubelike catheter, permanently implanted into the abdominal cavity, is used to inject up to 3 liters of waste-absorbing fluid into the cavity, where it remains for anywhere from two to six hours before it needs to be drained. The process must be performed four to six times per day, or patients can use a mechanical device, called a "cycler," overnight.
In hemodialysis, a patient's vein or catheter tubing is used to pump blood outside of the body and through a machine, called a dialyzer, which filters out waste. The cleansed blood is then pumped back into the body. The treatment lasts approximately three to four hours, and needs to be performed approximately three times per week at a dialysis center or appropriate health clinic.
Initial results showed that during the first year of treatment, patients choosing peritoneal dialysis were doing as well as patients on hemodialysis. Death rates early in the study were 21 percent and 24 percent, respectively, which were not different enough to be significant, statistically speaking. However, the Hopkins team noted that patients starting treatment with peritoneal dialysis were healthier overall, and more of them had graduated from high school, were married, or had jobs than those on hemodialysis.
When these differences were taken into account, the researchers discovered that while healthy patients did well on either form of dialysis, hemodialysis was of greater benefit for those patients with coexisting illnesses, such as cardiovascular disease. The risk of death among 135 patients with cardiovascular disease who were using peritoneal dialysis was nearly twice that of 459 similar patients on hemodialysis. After one year of dialysis treatment, the risk of death for patients who started on peritoneal dialysis was greater than the risk of death for patients who started on hemodialysis.
"Our results show that there is clearly a benefit in choosing hemodialysis over peritoneal dialysis, particularly for patients suffering from cardiovascular disease," says the study's principal and senior investigator, Neil R. Powe, M.D., M.P.H., M.B.A., a professor and director of the Welch Center for Prevention, Epidemiology and Clinical Research at Hopkins. "Patients who initially select peritoneal dialysis should be monitored carefully for a timely switch to hemodialysis, when peritoneal dialysis does not work as well anymore."
Funding for this study, which took place from October 1995 to December 2002, was provided by the Agency for Healthcare Research and Quality, and the National Institutes of Health, including the National Institute of Diabetes and Digestive and Kidney Diseases, and the National Heart, Lung and Blood Institute.
Other investigators in this research were Josef Coresh, M.D., Ph.D.; Laura Plantinga, Sc.M.; Nancy Fink, M.P.H.; Michael Klag, M.D., M.P.H.; Andrew Levey, M.D.; Nathan Levin, M.D.; John Sadler, M.D.; and Alan Kliger, M.D.