When this test applies
Required wherever the device contacts circulating blood, under ISO 10993-1:2025. ISO 10993-4 does not prescribe one test — it sets out which blood-interaction categories apply to which device type, and coagulation time is one of them. It is the coagulation arm of the ISO 10993-4 battery, and it matters for any device in the blood path where either accelerated clotting or impaired clotting would be a clinical problem.
When to run it
After cytotoxicity, and once the material set and surface finish are settled. Blood interaction is sensitive to surface topography and to processing residues, so running it on a material you still intend to change tends to buy a result you have to repeat.
What a pass tells you
That the device neither significantly shortens nor significantly prolongs PTT relative to the concurrent negative control. Both directions matter: shortening points at a procoagulant surface, prolongation at interference with the cascade.
What it does not tell you
PTT covers the intrinsic pathway. It is not a thrombosis model — it says nothing about platelet adhesion, thrombus formation under flow, complement, or hemolysis. ISO 10993-4 may call for several of the blood-interaction tests together, and a pass on one says nothing about the others.
Method
Testing per ISO 10993-4:2017. Human platelet-poor plasma is exposed to the device or a representative sample and clotting time is measured against the concurrent negative control. Where a representative sample rather than the whole device is used, extraction ratios follow ISO 10993-12: 6 cm²/mL for material under 0.5 mm thick, 3 cm²/mL at 0.5 mm or thicker, or 0.1 to 0.2 g/mL where surface area is indeterminate.
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 cover, in Groenakker’s report template or in your document template on request at no extra cost.
Usually ordered alongside
Platelet and leukocyte counts, complement activation and hemolysis. A biological evaluation plan is the cheapest way to establish which of the six hemocompatibility tests your device actually needs.
