Switching and the definition of modality in end-stage renal disease treatment.

End-stage renal disease treatment expenditures have increased greatly in recent years. Modality of treatment is a very important factor in determining costs as well as outcome and quality of life. Using quarterly observations on treatments received by ESRD patients, this paper presents a definition of modality based on type of treatment received and setting in which treatment is received. This paper also documents the magnitude of switching among defined modalities. Because many patients switch modality, selection of one modality is really a selection of a probable course of treatment by several modalities. The careful definition of modality and recognition that switching occurs are important first steps in conducting cost-effectiveness type analyses of ESRD treatment.