by Amy Karren, Microbiology Section Leader, SM(NRCM), Nelson Laboratories
Bacterial endotoxin can be introduced to the human body by medical devices and pharmaceutical products through direct or indirect contact with blood, lymph nodes, and with cerebral spinal or brainstem contact if they are not properly manufactured or cleaned. Bacterial Endotoxin Testing is also referred to as the Limulus Amebocyte Lysate (LAL) Test. Bacterial endotoxin contamination can present high fever and potentially cause death among humans.
The bacterial endotoxin test process involves washing or flushing the, medical device, which is referred to as an extraction. The extraction liquid is then mixed with the LAL reagent. The formation of a clot, increase in turbidity or color change of the LAL reagent indicates the presence of endotoxin. If there is no reaction the detected endotoxin will be reported as less than the assay sensitivity (test sensitivity multiplied by the extraction volume). All parts of the device that will come into contact with the human body should be included in the analysis.
Since Gram negative bacteria, which produce endotoxin, are dangerous to the human body in either a dead or living state, it is imperative medical device manufacturers conduct bacterial endotoxin testing on their medical devices in the finished form. Testing may be performed before or after the sterilization process. We recommend testing pre-sterile for those devices that undergo radiation sterilization—to ensure minimal delay in getting the device shipped to market. The validation study should reflect whether the devices evaluated were pre or post the sterilization process. Traditional industrial sterilization generally does not reduce the bacterial endotoxin content on or in product.
Endotoxin does not have an effect on the body when taken orally, the testing is only necessary on devices that will come in contact with blood, lymph nodes, and cerebral spinal or brainstem contact. The FDA also mandates that manufacturers to test devices that come in contact with the vitreous fluid of the eye.
The recommended sample size is 3-10 devices to be pooled from each batch. Alternatives to batch testing may be defined and justified, in accordance with guidance given in AAMI ST72. If in the test there are failures (endotoxin is present) then manufacturers should look at their manufacturing process for endotoxin contributors such as raw materials, humans, water (which is the main source of Gram negative bacteria), and the environment.
Bacterial Endotoxin Testing (LAL Testing) allows manufacturers to have confidence their devices are compatible with the human body and free of bacterial endotoxin.