Tuesday, March 10, 2009

Trial data confirms effects of S. aureus on mortality, costs of dialysis patients
By Maggie De Pano, DCRI Communications

Dialysis technicians generally avoid using catheters on kidney failure patients. Compared to other types of vascular access, catheter access is more prone to infection because it involves a persistent opening through the skin. DCRI researchers found evidence, however, that once patients are infected with Staphylococcus Aureus (S. aureus) bacteria, they experience similar outcomes regardless of the type of access used.

The study was published February 2009 in the Clinical Journal of the American Society of Nephrology. Shelby D. Reed, PhD, of the DCRI's Center for Clinical and Genetic Economics, is the senior author.

Dialysis removes waste products and excess water from the blood of patients with kidney failure. A dialysis machine can access blood in three ways. First, a catheter with two lumens may be inserted into a large vein so blood can flow through one lumen, enter the machine, then flow back the other. Second, an artery and vein may be fused to create an arteriovenous (AV) fistula. Two needles are inserted into this fistula during treatment, one to draw blood and one to return it. Third, an artery and vein may be joined using a synthetic tube to form an AV graft. This graft can then be used for needle placement.

Shelby’s team examined 3,359 dialysis patients enrolled between January 2004 and May 2005 in a large, multi-center, randomized clinical trial designed to evaluate the safety and efficacy of an S. aureus vaccine. S. aureus is one of the four most common causes of hospital-acquired infections. Frequently found in the nose and skin, it can lead to life-threatening conditions such as sepsis if it enters the bloodstream.

The researchers found that 279—or one in 12—of the patients developed S. aureus within a one-year period. None of the patients were using catheters when they enrolled in the study.

The researchers then collected complete hospital billing information for 176 patients who were hospitalized at least once for S. aureus infection. After excluding patients who were hospitalized for pneumonia or urinary tract infection and including only initial hospitalizations, they analyzed 159 patients' hospital bills. They divided these patients into two groups: patients with bacteremia, or S. aureus in the blood (89 patients), and patients with no S. aureus in the blood (70 patients).

They found that over a period 12 weeks, 20.2 percent of patients with bacteremia died. This group also incurred an average of $19,454 in hospital costs and spent an average of 11.9 days in the hospital. Meanwhile, 15.7 percent of patients without bacteremia died. This group incurred an average of $19,222 in hospital costs and spent an average of 11.3 days in the hospital. The researchers also found that older patients with bacteremia were more likely to die, while older patients without bacteremia were more likely to incur higher hospital costs and spend more days in the hospital.

Shelby’s team noted that using robust data from a large, randomized clinical trial confirms that despite the lower risk of infection associated with avoiding catheters, S. aureus, once it develops, still significantly affects the mortality and hospital costs of dialysis patients. The researchers encouraged more interventions to reduce S. aureus infection in this population and ultimately lighten the burden associated with end-stage renal disease.

Other DCRI researchers involved in the study include Yanhong Li, Joelle Y. Friedman, Betsy F. O’Neil, Martin E. Stryjewski, Kevin A. Schulman, MD, and Vance G. Fowler Jr., MD, MHS.

Click here to read the full study.