The reason the bacterial endotoxin test is also called LAL or limulus amebocyte lysate testing is because the lysate from blood cells (amebocytes) from horseshoe crabs (the latin name is limulus Polyphemus).  The lysate from the horseshoe crabs blood cells react with bacterial endotoxins.

Samples are mixed with the LAL reagent in a 96 well plate and a plate reader measure the color change over time.  The liquid in the wells becomes more yellow over time and the rate of that color change is proportional to the amount of endotoxin present in the sample. The impact of inhibitory compounds has less of an impact using the kinetic chromogenic method than other methods.  In addition, the kinetic chromogenic method is more sensitive than other LAL testing methods.

Product Types

All injectable pharmaceutical products and implantable medical devices need to be tested to ensure there is no presence of endotoxin, which can lead to a pyrogenic response (fever) and symptoms of septic shock. Endotoxins can be detected in these products and devices through bacterial endotoxin testing (BET). The most popular bacterial endotoxin test uses LAL (limulus amebocyte lysate) to test for bacterial endotoxins. 

Validation of bacterial endotoxins

The purpose of the validation of bacterial endotoxins is to check the sensitivity of the lysate in the presence of the product to ensure that it does not differ significantly from its sensitivity in the absence of it. In other words, the proposed product does not present interference factors which may result in false negatives or false positives, this taking into account the maximum dilution at which samples can be determined.

Routine Determination

The bacterial endotoxin test should be performed after each sterilisation cycle. In order to obtain a critical view, it is recommended to take samples for testing at the beginning, middle and end of the final assembly.