Cost Drivers of Endothelial Keratoplasty: A Time-Driven Activity-Based Costing Analysis

Abstract

To determine cost drivers of endothelial keratoplasty (EK) through evaluation of surgical costs and procedure length based on type of EK, use of preloaded grafts, and performance of simultaneous cataract surgery. This study was an economic analysis of EKs at a single academic institution using time-driven activity-based costing methodology (TDABC). EK surgical cases, including Descemet Membrane Endothelial Keratoplasty (DMEK) and Descemet Stripping Automated Endothelial Keratoplasty (DSAEK), at the University of Michigan Kellogg Eye Center from 2016 to 2018 were included in the analysis. Data and inputs were obtained via the electronic health record and from prior literature. Simultaneous cataract surgeries were included and separately categorized for analysis. EK expenses were determined with TDABC, a method for cost calculation that incorporates the time that key resources are used and each resource's associated cost rate. Main outcome measures included surgery length (in minutes) and day-of-surgery costs. There were 559 EKs included, 355 DMEK and 204 DSAEK. Fewer DSAEKs had simultaneous cataract extraction (47, 23%) than DMEK (169, 48%). Of the DMEKs, 196 (55%) utilized preloaded corneal grafts. DMEK cost $392.31 less [95% confidence interval ($251.05, $533.57), P < 0.0001] than DSAEK and required 16.94 fewer minutes [(14.16, 19.73), P < 0.0001]. DMEK cases that utilized preloaded corneal grafts cost $460.19 less [($316.23, $604.14), P < 0.0001] and were 14.16 minutes shorter [(11.39, 16.93), P < 0.0001]. In multivariate regression, preloaded graft use saved $457.19, DMEK (compared to DSAEK) saved $349.97, and simultaneous cataract surgery added $855.17 in day-of-surgery costs. TDABC cost analysis identified a day-of-surgery cost and surgical time reduction associated with the use of preloaded grafts for DMEK, DMEK compared to DSAEK, and isolated EK compared to EK combined with cataract surgery. This study provides an improved understanding of surgical cost drivers and margin incentivization, which may explain trends and indirectly influence patient care decisions in cornea surgery practices.