Timing of arteriovenous fistula placement and Medicare costs during dialysis initiation

Abstract

Background/aims: Arteriovenous fistulas (AVFs) appear to be clinically superior to catheters as vascular access for maintenance hemodialysis, but higher insertion costs and high disease burden and mortality obscure the issue of whether AVF placement before hemodialysis initiation represents a net cost savings. We aimed to investigate Medicare costs for patients beginning maintenance hemodialysis, as related to timing of AVF placement.

Methods: Data were from Medicare claims for incident hemodialysis patients aged ≥67 years in 2006. The study period extended from 2 years before to 1 year after dialysis initiation. Patients identified as having AVFs were categorized by timing of placement (mature AVF at dialysis initiation, maturing AVF at initiation, postinitiation AVF placement). Because timing may be influenced by factors that also influence overall costs, the model accounted for this nonrandom treatment assignment. An ordered probit extension of the classic Heckman correction was employed after identifying an appropriate instrumental variable. A cohort with Medicare coverage before and after dialysis initiation was identified, and Medicare claims were used to identify comorbid conditions and treatment costs.

Results: Principal findings are that earlier AVF placement leads to lower costs, with the potential for about USD 500 million in savings. Additionally, the effect of nonrandom treatment assignment is real and significant. In our data, the impact of AVF placement timing was understated when treatment selection was ignored.

Conclusions: For appropriate AVF candidates, having a mature AVF in place at the time of dialysis initiation appears to confer cost savings.

Figure 1

Timing of Medicare claims used to identify comorbidity and to calculate costs.

Figure 2

Mean predicted cost from ordinary least squares vs. selection corrected models. AVF, arteriovenous fistula; OLS, ordinary least squares.