Written by The Food and Drug Administration regulates all biologicals, medical devices, and parenteral drugs. They monitor the quality of the products and review changes to the products they approve. Products that will contact blood or cerebrospinal fluid must have endotoxin test results. The amount of endotoxin in the sample should be at or above a certain threshold, or the test will not be practical.
The test method for endotoxins is not standardized. There are many methods for determining endotoxins, including USP 85 and 161. In the USP, the Bacterial Endotoxin Test was revised in 1983 to improve its performance. However, the standard does not include any retest provisions, and many laboratories are still testing products to determine whether or not they are endotoxic. For these reasons, the test is only recommended for a single product.
There are several different endotoxin tests available. The LAL test uses the same reagent as the USP endotoxin tests. Nonetheless, the LAL test is more specific, and it can detect endotoxins in larger dosage units. It is also advisable to perform a USP chromogenic method for a final product. The USP chromogenic method measures serine protease activation, which is critical in the clotting cascade.
There are two types of endotoxins available, a synthetic lipopolysaccharide and a biotoxin. A polymer is a heat-stable lipopolysaccharide. These peptides are attached to the outer membrane of some gram-negative bacteria. When released into the bloodstream, they can cause serious clinical problems and death. The endotoxin units are measured compared to the USP Reference Standard Lot EC-5. The USP Endotoxin Test is used to determine whether or not the product contains endotoxins.
An accredited laboratory performs a LAL test to determine whether or not a particular product contains endotoxins. A LAL test requires the use of pyrogen-free labware. The LAL reagent must be pH-free. Various other factors may interfere with the LAL test, including the concentration of proteins and other interfering chemicals. For these reasons, a LAL test is not recommended for medical devices.
Atlantic horseshoe crab blood cells contain a clotting factor, which triggers the formation of clots in the presence of endotoxin. This enzyme is produced in the horseshoe crab's blood and binds endotoxin in the blood. The USP has accepted this method since 1983. Its results can be used to determine whether a product contains any endotoxins.
The endotoxin test can be performed by comparing the sample with a lysate. Lysates are a liquid solution of bacteria and are based on the physiological reaction between the endotoxin and a clotting enzyme. The active clotting enzyme then converts it to a coagulation protein. The disulfide bonds are detected through spectrophotometry.
