EN ISO 10993-11: Pyrogenicity tests and safety protocols for medical devices
When evaluating the biocompatibility of medical devices, ensuring the systemic safety of the patient is the main goal. The EN ISO 10993-11 standard deals with the systemic toxicity and in particular the pyrogenicity (fever-causing effect) of substances that can leak from medical devices.
Pyrogens are substances that, when entering the body, stimulate the immune system and can lead to fever, inflammation and, in severe cases, septic shock.
Types and sources of pyrogens
Pyrogens can basically be divided into two categories:
- Endotoxins (bacterial pyrogens): These are lipopolysaccharides (LPS) that are found in the cell wall of gram-negative bacteria. They are very heat-resistant, so endotoxins can remain on the product even if sterilization kills the bacteria.
- Material-related pyrogens (MP): Non-bacterial pyrogens that come from the raw materials of the device or chemical residues from the manufacturing process.
Pyrogenicity test method according to EN ISO 10993-11
The standard provides various methods for measuring the pyrogenic potential of a device. The choice of test depends on the duration and type of contact of the device with the body.
1. Rabbit Pyrogen Test (RPT)
This is the traditional and most comprehensive method. It can detect bacterial endotoxins as well as material-related pyrogens.
- Procedure: The extract of the test sample is injected intravenously into rabbits and the change in the animals' body temperature is observed.
- Advantage: Reacts to all types of pyrogens.
2. Bacterial endotoxin test (LAL test)
Used only to measure endotoxins from gram-negative bacteria.
- Procedure: A reagent is used that is obtained from the blood cells of the horseshoe crab (Limulus polyphemus).
- Limitation: Material-related pyrogens (chemical residues, etc.) cannot be detected.
3. Monocyte activation test (MAT)
It is an "in vitro" process (in the laboratory) that uses human blood. It was developed as an alternative to animal testing.
- Procedure: It measures the cytokines (e.g., $IL-1\beta$ or $IL-6$) released by human monocytes upon contact with pyrogens.
- Meaning: It is the test that best simulates the human immune system.
| Test procedure | Target Pyrogen Type | System Type |
| Rabbit Pyrogen Test (RPT) | Endotoxin + Material Source | In vivo (Alive) |
| Bacterial endotoxin test (LAL test) | Bacterial endotoxin only | In vitro (biochemical) |
| Monocyte Activation Test (MAT) | All Pyrogens | In vitro (cellular) |
EN ISO 10993-11: Pyrogenicity tests and safety protocols for medical devices
When evaluating the biocompatibility of medical devices, ensuring the systemic safety of the patient is the most critical step. The EN ISO 10993-11 standard deals with the systemic toxicity and in particular the pyrogenicity (fever-causing effect) of substances that can leak from medical devices.
Pyrogens are substances that, when entering the body, stimulate the immune system and can lead to fever, inflammation and, in severe cases, septic shock.
Types and sources of pyrogens
Pyrogens can basically be divided into two categories:
- Endotoxins (bacterial pyrogens): Lipopolysaccharides (LPS), which are found in the cell wall of gram-negative bacteria. They are very heat-resistant, so endotoxins can remain on the product even if sterilization kills the bacteria.
- Material-related pyrogens (MP): Non-bacterial pyrogens that come from the raw materials of the device or chemical residues from the manufacturing process.
Pyrogenicity test method according to EN ISO 10993-11
The standard provides various methods for measuring the pyrogenic potential of a device. The choice of test depends on the duration and type of contact of the device with the body.
1. Rabbit Pyrogen Test (RPT)
This is the traditional and most comprehensive method. It can detect bacterial endotoxins as well as material-related pyrogens.
- Procedure: The extract of the test sample is injected intravenously into rabbits and the change in the animals' body temperature is observed.
- Advantage: Reacts to all types of pyrogens.
2. Bacterial endotoxin test (LAL test)
Used only to measure endotoxins from gram-negative bacteria.
- Procedure: A reagent is used that is obtained from the blood cells of the horseshoe crab (Limulus polyphemus).
- Limitation: Cannot detect material-related pyrogens (chemical residues, etc.).
3. Monocyte activation test (MAT)
It is an "in vitro" process (in the laboratory) that uses human blood. It was developed as an alternative to animal testing.
- Procedure: The cytokines (e.g. IL−1β or IL−6) that are released by human monocytes when they come into contact with pyrogens are measured.
- Meaning: It is the test that best simulates the human immune system.
Why is the pyrogenicity test necessary?
For medical device manufacturers, these tests are not only a legal requirement, but also a risk management strategy. They are particularly important for the following product groups:
- Cardiovascular implants
- Intravenous catheters
- Drug Delivery Systems
- All surgical instruments that come into contact with blood
Note: The fact that a device is "sterile" does not mean that it is "non-pyrogenic". Sterilization kills microorganisms, but does not always remove pyrogenic residues.