Understanding ASTM F2638

By Daphne Allen in Testing on August 26, 2015

As one of the independent laboratories testing packages and materials in the Medical Packaging Transition Project (MPTP) for DuPont Tyvek, Nelson Laboratories has deepened its knowledge of ASTM F2638, “Standard Test Method for Using Aerosol Filtration for Measuring the Performance of Porous Packaging Materials as a Surrogate Microbial Barrier,” company representatives report. The test method is a newer method for testing microbial barrier properties that offers an alternative to ASTM F1608, “Standard Test Method for Microbial Ranking of Porous Packaging Materials (Exposure Chamber Method).” Nelson Labs has been performing pre- and post-sterilization packaging and material evaluations of all packaging formats submitted for the MPTP by medical device manufacturers.

DuPont seeks to demonstrate that Tyvek 1073B and Tyvek 1059B made with its latest flash-spinning technology is functionally equivalent to Tyvek manufactured with existing technology. The results that DuPont has reported to date do demonstrate functional equivalence or even better performance, and the company does expect U.S. FDA affirmation of functional equivalence in September 2015.

Nelson Laboratories has tested thousands of samples for microbial barrier properties. In the Webcast, "The Results Are In: DuPont Publishes First Tyvek Transition Package Data DuPont reported that the Transition Protocol material is functionally equivalent to current Tyvek in terms of pre and post-sterilization microbial barrier performance.

DuPont has also reported that it has submitted confidential MPTP regulatory reports to the U.S. FDA, Health Canada, and five notified bodies. It has also posted publically new data summaries and documents to its Web site. 

One of the methods DuPont has used to show equivalency is ASTM F2638, reports Jennifer Gygi, packaging department scientist for Nelson Laboratories, and she believes that this method is the direction the industry is going in terms of microbial barrier testing. Craig Fisch, packaging department study director for Nelson Laboratories, points to ASTM F2638’s “speedy results.” Gygi says that test results can be generated within an hour, and that same-day reports are available upon request. 

In addition, “you don’t have to worry about microbial incubation with ASTM F2638, because you are using latex spheres or particles counted in real time with laser particle counters to get the porous material’s filtration efficiency,” Fisch says. “You are also testing at real-world flow rates instead of the very high flow rates associated with F1608.” 

However, “there is not a lot of comparative data on this test method because it is a fairly new method, so companies are still learning about it and trying it out,” he says. 

“We are in a unique position where we have both offerings, and we can compare the differences between the two,” added Gygi. “We’ve been doing both for a number of years and have a pretty good handle on the advantages and disadvantages between the two methods [F2638 and F1608].” 

ASTM F2638 is up for revision, and Fisch and Gygi state that based on the MPTP experience Nelson Labs is providing input to the committee for the revision.

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