Transitioning between Alternative Bacterial Endotoxins Tests (BETs)

When determining the best process for transitioning from one BET to another, note that the recombinant Horseshoe Crab factor C assay requires validation under the USP section , Validation of Compendial Procedures. It must be demonstrated that equivalent or better results, as compared to a compendial test, can be achieved. Additional work may be required based on one’s risk management program. Some of these are recommendations regarding sampling and testing of medical devices. Other procedures or testing regimens can be used. However, the appropriateness of the procedures must be justified.

The FDA states: “For devices, a 30-day notice may be appropriate for changes to quality control testing used in incoming components, raw materials, inprocess devices, or finished devices, including performing end-product pyrogen testing on non-sterile samples prior to sterilization.”

Endotoxin Limits

The limits for endotoxin stated in the USP 35 2012 chapter 161, Transfusion and Infusion Assemblies and Similar Medical Devices, depend on the route of administration, the intended use of the device, and what the device contacts: blood, cardiovascular system, lymphatic system, cerebrospinal fluid, intrathecal routes of administration, permanently implanted devices, and devices implanted subcutaneously. (See Table 1)

The FDA has added some information that can be confusing to the non-practitioner. The process of preparing eluate/ extract from the devices can vary widely with each device configuration. This can include:

A. Flushing the device: catheters that the internal surfaces are labeled non-pyrogenic

B. Disassembly or cutting up devices into pieces: devices that are too big to be adequately rinsed

C. Immersion: implantable devices

The QC lab generally will recommend the appropriate eluate/extract technique. The guidance indicates that labs can test the surface area that contacts the patient. One can use an adjustment factor to determine limits. However, generally 40 mL of non-pyrogenic water is used to rinse the device. Ten units are recommended in their guidance document. Using more than 40 mL per device requires a submission.

The FDA has also indicated that one should evaluate multiple units of the same device used in a procedure. The devices must meet the same endotoxin limit as a single device; for example: 20 EU/device or 0.5 EU/mL.

The FDA is also requesting 510k premarket notification submissions when the firm is deviating from the new guidance or recognized standard. Significant deviations include: sampling fewer than three lots for inhibition enhancement testing; using a lesser sensitivity to endotoxins; using more than 40 mL per device for rinsing without adjusting the dilution factor, which would cause a greater dilution than the guidance document allows.

Quality by Design (QBD)

Quality by design (QBD) concepts can support endotoxin limits. The goals of product and process risk assessments are to provide a consistently non-endotoxic product. Firms need to evaluate raw material or in-process testing. When the process is considered a wet process, QA should review the critical control points and validate the propensity for endotoxin contamination. QA teams may be required to add this as part of QBD programs. That means quantitative testing (i.e., setting alert and action limits for in-process materials) is preferred by the FDA over limit testing. This type of approach will prevent excursions before they happen and prevent a recall. The FDA will be evaluating the endotoxin limit approach submitted with each new device. A strategy for setting limits is justified. QBD programs should be instituted in most production environments.

In the agency’s new Guidance document, the FDA provides direction on what is acceptable and reveals some color on the sampling requirements and quality- by-design concepts. QBD risk management, according to ISO 10993-1:2009 Biological Evaluation of Medical Devices Part 1: Evaluation and Testing in the Risk Management Process, would require device management to increase testing and sampling targets for wet manufacturing processes. Utilizing the quantitative approach to endotoxin testing will, for the majority of affected medical device manufacturers, provide the most beneficial route to compliance.

This article was written by Steven G. Richter, PhD, President and Chief Scientific Officer of Microtest Laboratories, Inc., Agawam, MA. He founded Microtest after a distinguished career at the U.S. Food & Drug Ad ministration. For more information, email This email address is being protected from spambots. You need JavaScript enabled to view it. or visit See Microtest Laboratories at BIOMEDevice, Boston, Booth 1010.