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A novel low volume blood loop model (Ension Triad System [ETS]) incorporating pulsatile flow and a proprietary low-activation blood-contacting surface (Ension bioactive surface [EBS]) enabling high signal-to-noise performance is described. The ETS system incorporates a test chamber that allows direct comparison of material samples or finished medical devices such as catheters with varying compositions and/or surface treatments. ETS performance is presented from two independent organizations (Medtronic and MLM Labs) and includes results for hemolysis (pfHgb), platelet count, platelet activation (βTG), coagulation (TAT), inflammation (PMN Elastase, PMN CD112b, and monocyte CD112b) and immune response (SC5b-9) were made on: (1) the EBS-treated system itself without a test material (No Material, NM); (2) the EBS-treated system with an idealized untreated catheter (UC); and (3) the EBS-treated system with the prototype catheter treated with the EBS surface treatment (CC). The untreated catheter (UC) was associated with significant elevation of all activation marker levels (pfHgb excluded). The EBS-treated catheter, in direct comparison to the UC and NM catheters, appeared invisible with respect to the activation markers (all markers statistically different than the UC and equivalent to the NM control). Based on these data, we conclude that using a relatively small surface area test sample and a small volume of fresh human blood, the high signal-to-noise performance of the ETS system demonstrates comprehensive and statistically significant material differences in the major ISO 10993-4 categories of blood interaction. These data underscore the important benefit of minimal confounding of test/device responses with non-test-material/model-related responses. ETS offers a practical alternative to the common one-test-category-at-a-time approach when assessing blood/medical device interactions., (© 2022 Wiley Periodicals LLC.)