CMS SOM App. H, Tag V258

7.2.4 Bacterial endotoxin test

At a minimum, two tubes should be run each time the assay is performed. The first tube

contains LAL reagent and the sample to be tested. The second tube contains LAL reagent,

a known amount of endotoxin, and the sample to be tested. The second tube acts as a

positive control to confirm the absence of any interference that might lead to a false

negative result.

Interpretive Guidance § 494.40(a)

ANSI/AAMI RD52:2004

7.2.4 Bacterial endotoxin test

Bacterial endotoxin testing is done using the Limulus amoebocyte lysate (LAL) assay. Two basic

types of assay can be performed. The first is a kinetic assay, which is available in a colorimetric

or turbidimetric format, and the second is a gel-clot assay.

The kinetic LAL assay uses control standard endotoxin to generate a standard curve to which

unknowns are compared and concentrations are determined using linear regression. The kinetic

assays employed in laboratories generally use a computer-driven spectrophotometer that

automatically calculates the amount of endotoxin on the basis of color development or onset

times for gel formation.

The gel-clot LAL assay is not as sensitive as the kinetic assay and provides only a positive or

negative result; that is, it shows if endotoxin is present—or not—at a particular concentration.

Single tube gel-clot tubes are available from several commercial sources, and kits with the

following sensitivities are currently available: 0.015 EU, 0.03 EU, 0.06 EU, 0.125 EU, 0.25 EU,

and 0.5 EU. Please note that these availabilities are subject to change, as technologies for

testing sensitivities advance with time.

Positive control tubes are available from the suppliers of commercial LAL assays. More

sophisticated testing protocols involving reagent controls may also be used (see 2.7), but their

use is optional in this application.

Additional Guidance:

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Technology for endotoxin testing is evolving and these regulations are not meant to prevent the

use of a newer testing methodology, once such methodology is approved by FDA.