Increasing the frequency of kidney dialysis or using different filters does not improve the outcome for patients.
The guidelines on kidney dialysis put forward by the US National Kidney Foundation involve treatment three times a week for three or four hours. But could patients do better - with more intensive treatment, or different equipment?

Researchers at Baylor College of Medicine in Houston have led a study that compared standard and high frequency dialysis, and also standard dialysis with treatment using a high flux filter. These comparisons involved over 1,800 patients in 15 medical centres. Overall, the standard regime is best. More frequent treatments do not improve survival or quality of life. Nor does the high flux filter - which remove large waste molecules from the blood - seem to confer any advantage.

However, there were some intriguing differences in sub-groups. Women seemed to do better on the more frequent treatment, while those who'd been on dialysis for a long time seemed to fare better on the high flux filters. Further work will evaluate the best dialysis regime for specific groups of patients.

Kidney failure - for which dialysis is the usual treatment - is an increasing problem in the US and elsewhere. But it could be avoided by keeping risk factors like diabetes and high blood pressure under better control. Then fewer people would need to be on dialysis.