Is it time to rebalance the case mix? A portfolio analysis of direct catheterization laboratory costs over a 5-year period

BACKGROUND: Cardiac catheterization laboratories (CLL) have continued to function as profit centers for hospitals. Due to a high percentage of material and labor costs, they are natural targets for process improvement. Our study applied a contribution margin (CBM) concept to evaluate costs and cost dynamics over a 5-year period. METHODS: We retrospectively analyzed all procedures performed at a tertiary heart center between 2007 and 2011. Total variable costs, including labor time, material, and maintenance-expenses, were allocated at a global as well as a procedural level. CBM and CBM ratios were calculated by integration of individual DRG revenues. RESULTS: Annual case volume increased from 1288 to 1545. In parallel, overall profitability improved as indicated by a 2% increase in CBM ratio and a higher CBM generated per hour of CLL working time (4325 vs. 5892 €, p < 0.001). Coronary angiography generated higher average CBMs per hour than coronary or electrophysiological interventions (5831 vs. 3458 vs. 1495 €; p < 0.001). The latter are characterized by relatively high per case material expenditures. On a procedural level, DRG-specific trends as a steady improvement of examination time or an increase in material costs were detectable. CONCLUSIONS: The CBM concept allows a comprehensive analysis of CLL costs and cost dynamics. From a health service providers view, its range of application includes global profitability analysis, portfolio evaluation, and a detailed cost analysis of specific service lines. From a healthcare payers perspective, it may help to monitor hospital activities and to provide a solid data basis in cases where inappropriate developments are suspected. The calculation principle is simple which may increase user acceptance and thus the motivation of team members. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s40001-016-0238-5) contains supplementary material, which is available to authorized users.