Introduction to the LAL Test
Limulus Amebocyte Lysate (LAL) tests detects and quantifies bacterial endotoxins extracted from the outer membrane of Gram-negative bacteria. The critical component of the LAL reagents used in endotoxin tests is derived from blood cells (amebocytes) of the horseshoe crab, Limulus polyphemus. It contains the proteins of the blood clotting mechanism, which is triggered by endotoxins. LAL reagents are primarily used to test for endotoxins in injectable pharmaceuticals, biological products, and medical devices. They are also used in renal dialysis centers and a wide range of other applications.
LAL tests are described in the Bacterial Endotoxins Test chapter in the United States Pharmacopeia and in the equivalent chapters in the European Pharmacopoeia and the Japanese Pharmacopoeia.
LAL Test Methods
There are three principal LAL test methods:
- Gel-clot – The original LAL assay and the method of reference in most reference manuals (maximum sensitivity 0.03 EU/mL).
- Turbidimetric – The most sensitive endotoxin test available in the industry (maximum sensitivity 0.001 EU/mL).
- Chromogenic – Color formation is used to quantitate endotoxin (maximum sensitivity 0.001 EU/mL) and glucans.