FDA/USP Gel Clot Testing
 Microtest gel clot testing detects bacterial endotoxin — cell wall material from Gram-negative bacteria. Since this material is pyrogenic, or capable of causing high fevers in humans, testing is recommended for injectable drugs and for medical devices that contact the blood.
Note that Microtest endotoxin assays include gel clot plus chromogenic and turbidimetric methods. All are sensitive, reliable, efficient, and usually recommended over the older, slower pyrogen test using rabbits. Call Microtest for information on which test best suits your particular product, and on standard protocols for sample preparation, shipment, and packaging.
As with all Microtest procedures, testing is performed by experienced microbiologists with state-of-the-art equipment. Our method follow procedures derived from the U.S. Food and Drug Administration (FDA) and United States Pharmacopeia (USP). Guidelines on end-product tests for endotoxin content are issued by the FDA and the Center for Devices and Radiological Health (CDRH) under 21 CFR Section 10.90 (b).
The gel clot method is based upon the reaction between bacterial endotoxin and a specific lysate, or content released from a cell. This particular lysate is derived from a rather exotic source: the circulating amebocytes associated with the blood-clotting mechanism of the horseshoe crab Limulus polyphemus.
Lysate is introduced to a sample of a given device. If a gel is formed via a clotting reaction, endotoxin is present and the sample fails the test. Test sensitivity depends on the lysate used. Gel clot testing’s lowest limit of detection (LLD) is 0.03 EU/mL, as compared to 0.005 EU/mL for the chromogenic and 0.005 EU/mL for the turbidimetric method.
Given the potential for patient harm, all Microtest endotoxin testing procedures are rigorous. Glassware used is controls-checked, and depyrogenated under our extensive Good Manufacturing Practices (GMP) program. Routine tests are run in duplicate, with inhibition/enhancement testing in triplicate. And the Control Standard Endotoxin (CSE) is tested against the USP Endotoxin Reference Standard (RSE).
Test results can usually be reported within 1 week.
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