Hemocompatibility: Hemolysis test. EN 10993-4: 2018. Biological evaluation of medical devices: Selection of tests for interaction with blood, and ASTM F 756-93 method.

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There are several tests that determine the hemocompatibility of a product, investigating its ability to induce thrombosis, coagulation, platelet activation, or activation of other biological systems. The hemolysis test determines the ability of a product, or an extract obtained from it, to cause hemolysis, using rabbit blood or human blood, by spectrophotometrically measuring the absorbance of assay mix to which the blood has been added, then to incubate at 37°C for 3 hours, as well as the corresponding negative and positive controls. A percentage of hemolysis below 2% is considered non-hemolytic, considering the value of 100% for the total amount of hemoglobin present in the added erythrocytes.

In the direct contact hemolysis test, the product is placed in direct contact with a saline suspension of rabbit blood. The percentage of hemolysis induced by the biomaterial is determined by spectrophotometrically measuring the hemoglobin released from the erythrocytes.

In the hemolysis test with extracts, the product is subjected to extraction with physiological buffered saline solution (PBS). A portion of the salt extract is added to a rabbit blood suspension, and mixed thoroughly. The percentage of hemolysis induced by the extract is determined by measuring the hemoglobin released from the erythrocytes by spectrometry.

The ASTM F756 Standard, recommends to perform both assays (the hemolysis test by direct contact and the hemolysis test with extract), unless that due to the use of the product one of the methods could be excluded.