A bacterial endotoxin test (BET) is a quality control assay used to detect and quantify endotoxins, which are toxins released from the outer membrane of gram-negative bacteria. Endotoxins on medical devices can be dangerous and may cause severe inflammatory responses and fever once they contact human tissue or are introduced to the bloodstream. BET is used to ensure the safety of device end users and the testing may be required to meet regulatory standards.
The bacterial endotoxin test is required for devices labeled as non-pyrogenic, as well as many pharmaceutical products. The United States FDA and the European Medicines Agency (EMA) require BET for certain medical devices, including: implants, devices that contact blood, and devices that contact cerebrospinal fluid.
The procedure for bacterial endotoxin testing includes four steps:
BET may be performed with LAL reagent in one of these three methods:
The gel clot method is a qualitative test. Formation of a gel clot indicates the presence of endotoxins.
This quantitative testing method measures turbidity increases caused by a reaction between endotoxins and LAL reagent.
The chromogenic method is also a quantitative test. Reactions between endotoxins and a chromogenic substrate in the LAL reagent cause a color change, indicating the presence of endotoxins.
Regulatory standards such as USP <161>, AAMI ST72, and ISO 11737-3 specify acceptable endotoxin limits for different types of medical devices. These limits may be defined as endotoxin units (EU) per device, EU per gram, or EU per milliliter.
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