Accelerated aging test tips

Larsen said, "One sample can't be used for both the sterile barrier system aging and design performance qualification testing, and expect consistent success. One of the objectives of the sterile barrier is to make sure it will maintain the sterility of the contents for the package's stated shelf life. To support those dating claims, you do an aging study to see what happens over time. We look at what happens to the materials and the seals between those two materials after they have been sterilized; that is all that needs to be done. You can use the same information on aging that others have, including details from suppliers that can provide data on the aging of their material combinations sterilized in different ways."

Larsen recommended that device manufacturers pay attention to materials and adhesives, and keep samples below 55º C for their accelerated temperature. He added, "Humidity has nothing to do with aging—it confounds the entire process and can cause reaction between materials that would normally never happen. If there's a need for humidity in testing, the selection of the correct materials is critical." He recommended referencing the F1980-07's new revision for guidance on humidity. Other Larsen tips:

• Understand that seals may get stronger over time. Most of the packaging materials used today are very robust, and can readily maintain package integrity for many years.

• Know your distribution environment. Canned tests may be more severe than the actual distribution environment.

• Inspect your sample during testing if possible--before and after sterilization—to learn where a failure happened.

• Consider that sample sizes may open a can of worms. Ten boxes of one dozen are not 120 samples, they are 10 samples. A sample is what goes out the door, what is introduced into interstate commerce. If a single device is sold as one, or in a quantity of one dozen, as a 24-pack, as a gross, as a pallet, you have five different products and five different packaging systems. If you choose one of those as a "worst-case" design to test and not test the others, you must justify why.

• Understand what stresses your sample will be subjected to during distribution. A pallet doesn't withstand nearly the beating as one package going through small-parcel distribution on its own. A multipack package system has different stresses on the contents than that of a one-each.

• Realize that sample sizes are a business decision because they can be quite expensive and tough to get. In general, 30 is a number that the FDA finds acceptable for accelerated aging, but if you sell 150 high-priced items a year, 12 might be a reasonable amount to sample in accelerated aging tests. Whatever your sample size is, you must document the rationale you used in selecting it.

--By Jim Butschli, Editor