New statistical method shows importance of dialysis dose

New statistical method shows importance of dialysis dose

'Accelerated failure time' model better explains survival rates in hemodialysis patients

A new approach to statistical analysis may be better suited to study the relationship between higher "dose" of dialysis and survival time for patients with advanced kidney disease, according to an upcoming paper in the Journal of the American Society of Nephrology (JASN).

Some studies have shown longer survival times for patients receiving a higher dose of dialysis, while others show no such relationship. Thus, Christos Argyropoulos, MD, PhD (University of Pittsburgh Medical Center) and colleagues analyzed data from a large group of U.S. dialysis patients using the new statistical technique as well as conventional methods.

The "accelerated failure time" model (inspired by considerations of what happens when kidneys cease working and many unidentified toxins start building up in the patient's bloodstream) showed longer survival times at a higher dose of dialysis, compared to no significant effect with the conventional model. Upon analysis using this technique, patient survival increased steadily along with dialysis dose, after adjustment for other risk factors (age, heart disease, diabetes, comorbid conditions, etc).

The results suggest that the conflicting results of previous studies may be related to the limitations of the statistical methods used. Small to moderately sized clinical trials may be particularly sensitive to this effect, adds Argyropoulos. "From a public health perspective, it may be reasonable to re-examine the clinical trial data with unconventional, yet scientifically valid statistical techniques and encourage relevant basic research in statistics and epidemiology to facilitate future clinical studies in this area."

The study was limited by the lack of follow-up information on the dose of dialysis the patients received at multiple clinic visits. "Consequently, no conclusions could or should be drawn about the validity of existing national and international guidelines concerning an adequate dialysis dose," says Argyropoulos. He also stresses that the findings cannot be generalized to non-U.S. patients.

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Co-authors included Chung-Chou H. Chang, PhD, and Mark Unruh, MD (University of Pittsburgh); Nancy Fink, MPH (John Hopkins University, Baltimore); and Laura Plantinga, MSc, and Neil Powe, MD (University of California, San Francisco). The research was supported by an unrestricted grant through the Renal Discoveries-Baxter Extramural Grant program from Baxter Healthcare International to the authors and by grants from the Agency of Healthcare Research and Quality (AHRQ), the National Institutes of Diabetes and Digestive and Kidney Diseases (NIDDK) and the National Heart, Lung and Blood Institute (NHLBI).

The study entitled, "Considerations in the Statistical Analysis of Hemodialysis Patient Survival," will appear online at http://jasn.asnjournals.org/ on July 30, 2009, doi 10.1681/ASN.2008050551.

The American Society of Nephrology (ASN) does not offer medical advice. All content in ASN publications is for informational purposes only, and is not intended to cover all possible uses, directions, precautions, drug interactions, or adverse effects. This content should not be used during a medical emergency or for the diagnosis or treatment of any medical condition. Please consult your doctor or other qualified health care provider if you have any questions about a medical condition, or before taking any drug, changing your diet or commencing or discontinuing any course of treatment. Do not ignore or delay obtaining professional medical advice because of information accessed through ASN. Call 911 or your doctor for all medical emergencies.

Founded in 1966, ASN is the world's largest professional society devoted to the study of kidney disease. Comprised of 11,000 physicians and scientists, ASN continues to promote expert patient care, to advance medical research, and to educate the renal community. ASN also informs policymakers about issues of importance to kidney doctors and their patients. ASN funds research, and through its world-renowned meetings and first-class publications, disseminates information and educational tools that empower physicians.

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