Use of standardized ratios to examine variability in hemodialysis vascular access across facilities

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The type of hemodialysis vascular access (catheter, fistula, graft) is an important determinant of patient morbidity and dialysis efficiency. The relative importance of patient versus provider factors in determining type of vascular access is unclear. We sought to develop a quality improvement tool that adjusts for differences in patient characteristics, thereby allowing examination of provider-related variability in types of vascular access used across facilities. We examined 15,339 patients from 216 chronic hemodialysis units in Indiana, Kentucky, Ohio, and Illinois and found that 20% of patients had catheters, 24% had fistulas, and 56% had grafts. Young, male, and white patients were more likely to have fistulas, whereas old, female, and black patients were more likely to have grafts. Diabetics were more likely to have catheters and less likely to have fistulas. New patients were more likely to have catheters and less likely to have grafts. A facility specific standardized catheter ratio (SCR), standardized fistula ratio (SFR), and standardized graft ratio (SGR) were calculated based on the actual number of patients with each type of vascular access divided by the expected number adjusted for patient characteristics. Facility SCRs ranged from 0.00 to 2.87. Of the 216 facilities, 38 (18%) had an SCR significantly less than 1.00, and 32 (15%) had an SCR significantly greater than 1.00. Similar variability was observed in SFRs and SGRs. In conclusion, the type of vascular access varies greatly across facilities. Use of standardized access ratios adjusted for patient characteristics may help providers examine processes of care that contribute to variability in access use. Analogous to the standardized mortality ratio, the SCR, SFR, and SGR should be effective quality improvement tools.