When this test applies
Required wherever the device contacts circulating blood, under ISO 10993-1:2025, and most useful where the device meets blood in motion — catheters, cannulae, extracorporeal circuits, vascular grafts and stents. ISO 10993-4 sets out which blood-interaction categories apply to which device type; the blood loop model addresses thrombosis under flow, which static direct-contact methods do not reproduce.
When to run it
After cytotoxicity, and once the material set, surface finish and any coating are settled. Thrombogenicity is sensitive to surface topography, coating integrity and processing residues, so running it on a material you still intend to change tends to buy a result you have to repeat. Run it with the other blood-interaction parameters your device category calls for, in one campaign.
What a pass tells you
That under flowing blood the device did not produce thrombus formation or changes in the measured blood-compatibility markers significantly greater than the concurrent negative control, with the positive control performing as expected. It is the closest in vitro evidence available that a blood-contacting surface behaves acceptably in circulation.
What it does not tell you
A blood loop result is a model of flow, not a clinical outcome, and it is run in anticoagulated blood, so it does not predict performance in every patient or every anticoagulation regime. It says nothing about hemolysis by extract, complement activation or immunology unless those parameters are measured within the same study. ISO 10993-4 may call for several blood-interaction tests together, and a pass on one says nothing about the others.
Method
Testing per ISO 10993-4:2017. The device or a representative sample is mounted in a closed loop containing fresh, anticoagulated human blood and circulated under controlled flow and temperature for a defined period, with negative and positive reference materials run in parallel. At the end of exposure the test article and loop are examined for thrombus formation and the blood is assessed for the compatibility markers specified in the study design. Where a sample rather than the whole device is used, the sample must represent the blood-contacting surface in its finished, sterilised condition.
Where it runs
This method is internationally sourced. The laboratory is ISO/IEC 17025 accredited and GLP certified, and the report is issued under Groenakker’s ISO 13485:2016 certified quality system, in Groenakker’s template or in your document template on request at no extra cost.
Usually ordered alongside
The other hemocompatibility parameters your device category calls for — hemolysis, complement activation, platelet and leukocyte counts and PTT — plus cytotoxicity as the baseline screen. A biological evaluation plan is the cheapest way to establish which blood-interaction tests are actually required for your device rather than commissioning all of them.
