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    Common Questions

    If your company requires gamma treatment for a medical device that is labeled sterile there are several standards you need to be familiar with that are produced by ISO (International Organization for Standardization) and AAMI (Association for the Advancement of Medical Instrumentation). These standards include: ISO 11137:2006 Parts 1 through 3 (Sterilization of health care products-Radiation- Part 1: Requirements for development, validation and routine control of a sterilization process for medical devices.; –Part 2: Establishing the sterilization dose; – Part 3: Guidance on dosimetric aspects); ISO 11607 Parts 1 and 2 (Packaging for terminally sterilized medical devices-Part 1: Requirements for materials, sterile barrier systems and packaging system; Part 2: Validation requirements for forming, sealing and assembly process) and finally AAMI TIR17:2008 (Compatibility of materials subject to sterilization). These documents are available from the ISO (www.iso.org) or AAMI (www.aami.org) websites. These standards will guide you through what your company is responsible for regarding sterilization. The TIR 17 standard will allow your company to compare different material outcomes after exposure to one round of a typical sterilization dose.

    Some common questions are answered by the FTSI Quality Director below. Please feel free to email any specific questions to slefrancois@ftsi.us.

    How do we choose a worst case product that is designated as a representative for a product family?

    According to 4.3.1.1 (ISO 11137-2:2006) – “The number and types of microorganisms on or in product shall be used as the basis for selecting product to represent a product family.”

    Translation: Your company should select a product to represent a family based on the product that could potentially have the greatest bioburden. For example, if you have a product with multiple parts and it is similar to a product with fewer parts the maximum number of components could potentially carry the highest threat for bioburden. So this maximum component product would be your company’s representative family member.

    Is there a limit to how many components can fall under one product family?

    There is no limit to the number of products that could fall under one family. As long as: 4.2.2 (ISO 11137-2:2006) – “Product shall only be included in a product family if it is demonstrated the product-related variables (please see ISO 11137-2:2006 in 4.2.1) are similar and under control.”

    Once a representative product family member has been validated what is the frequency that is should be validated again?

    Once a representative product family member has been completed a validation for sterilization dose does not have to be completed again unless there are changes made to the representative product family member that would require a revalidation. Even if changes are made to the packaging or to the product your company can simply evaluate the change in bioburden on your product. If there is no significant change in bioburden (significant defined as an increase in bioburden that would affect your validation dose) your company can justify not repeating a validation be citing the bioburden data collected.

    If your company uses a simulated product to represent a large family of products ISO 11137-2 section 4.4.1 states that a periodic “review shall be performed at a specified frequency to assure that product families and product used to represent each product family remain valid. Responsibility for reviews of product and/or processes that might affect membership of product families shall be allocated to competent personnel. Such review shall be performed at least annually. The outcome of the review shall be recorded…

    Are there different levels of sterilization that customers expect? Such as “guaranteed sterilized”?

    There is not a level of sterilization. Something is either sterile or non-sterile. There is a “sterility assurance level” also known as an SAL which is defined as: “probability of a single viable microorganism occurring on an item after sterilization. The term SAL takes a quantitative value, generally 10-6 or 10-3. When applying this quantitative value to assurance of sterility, an SAL of 10-6 has a lower value but provides greater assurance of sterility than an SAL of 10-3.”

    Translation: During a validation, your product sterilization will be validated to a SAL of 10-6. This kill level of SAL 10-6 is obtained under the VDmax validation at a 25kGy or 15 kGy minimum dose.

    How fast can your company get this process up and running?

    A validation typically takes two weeks for bioburden determination and an additional two weeks for sterility testing from a laboratory. After about a month your company can have a sterilization validation and be able to begin treating product.

    Does it make sense for our sites to use one sterilizer or can the same process by used with any sterilizer?

    The great thing about gamma (as opposed to ethylene oxide sterilization) is that one validation can be carried to whatever sterilizer your company wishes to use. Once a gamma validation has been performed it does not have to be repeated. You would have to validate that new sterilizer (a radiation source other than that on which the dose was originally established) by performing a Performance Qualification (PQ= dose map) and initially performing a dose audit according to the transference of verification dose or sterilization dose (8.4.2 ISO 11137-1: 2006). However, FTSI has exceptional service and knowledge. If your company were to use FTSI we would not disappoint.

    When is there a need to complete a dose mapping?

    A dose map is needed to determine where the minimum and maximum amounts of radiation are absorbed in your product. The Operator would place dosimeters (small pieces of plastic that darken with increased exposure to gamma) all over your company’s pallet in a three dimensional pattern. The dosimeters are read at the end of processing to ensure your product has received the amount of radiation your company has specified.

    Dose mapping would be completed when you send new product to be sterilized at our facility. Dose mapping would also be performed if your company changed the density and/or multiples of your product in any way. For example, a dose map would be performed if your company changed the box dimensions and weight from the original dose map performed. Finally, a dose map would occur if FTSI changed their source amount or configuration in any way. (This dose map would not have to be paid for by your company.)

    How do we avoid shipping issues (damaged product) with sterilized product? Are there certain carriers that specialize in shipping sterilized products?

    Unfortunately, shipping issues can occur with sterilized products. There are not special carriers that ship sterilized products. According to ISO 11607-1:2006 section 6.3 Packaging-system performance testing: “The packaging system shall provide adequate protection to the product through the hazards of handling, distribution and storage.” and “Performance testing shall be conducted on the worst-case sterile barrier system produced at the specified process limits of forming and sealing and after exposure to all the specified sterilization processes.”

    When you determine your maximum dose that your product can withstand you should try to perform two times or three times the maximum dose tests in case your packaging is breached during shipment. This way you can sterilize your item again knowing that is can withstand that amount of radiation. This second sterilization will affect your shelf-life and therefore aging studies should accompany your two times or three times maximum dose determination. (Aging is 6.4 of ISO 111607-1:2006-Stability testing)

    What is the shelf life of a sterilized part?

    The shelf life will be determined by aging studies according to ISO 11307-1:2006, 6.4.3: “Stability testing, using accelerated aging protocols, shall be regarded as sufficient evidence for claimed expiry dates until data from real time aging studies are available.” Also, 6.4.4 “Real-time and accelerated aging tests should begin simultaneously.”

    Is it critical that parts be oriented the same every time in packaging when sent to a gamma sterilizer?

    For irradiation treatment purposes (since density is an important variable) it is important that your boxes be packaged in a uniform manner every time your company sends product for treatment in order to achieve uniform dose distribution.

    If this question pertains to packaging studies under the Design section 7.2 ISO 1137-1:2006: “Changes to product, product package or configuration of product within the package shall be specified (see 12.5.2).”

    12.5.2 states that “A change in product, its package or the presentation of product for sterilization shall be assessed for its effect on the appropriateness of the sterilization process…

    What are the top 3 to 5 items we should be looking for in a gamma/sterilizing company?

    What materials cannot be gamma treated?

    Your supplier should have information as to whether or not a particular component can be gamma sterilized. AAMI standard TIR17: Compatibility of materials subject to sterilization, lists materials and how they react to gamma as well as other methods of sterilization. However, the best answer to this question is to try to treat the product and determine if there is any yellowing, brittleness, increase in adhesive strength, etc. that might occur before committing to that material.

    What materials break down quicker after gamma?

    According to TIR17: PTFE (Fluoropolymers), PFA (Flouropolymers), Polyacetals (eg. Polyoxymethylene), and Butyl (Elastomers) react poorly to radiation.

    Does gamma ever fail? Can the exposure dots fail?

    Gamma will only fail if 1) the initial validation performed to determine the minimum sterilization dose was incorrect. 2) There is a spike in bioburden (to very high levels as compared to normal levels) on the product when it arrived at the sterilization facility for treatment. 3) The correct dose was not applied by the sterilizer. 4) The product was allowed to be re-contaminated after treatment.

    Exposure dots can turn color with high heat making it seem as if the product was treated when it was not. Or the dots could be from a failed lot and the color change would not occur.

    How is the amount of radiation exposure measured?

    The amount of radiation absorbed by a customer’s product is measured with dosimeters. Dosimeters are plastic pieces of material that darken with increased exposure to gamma. Dosimeters will be placed on product each time it comes to our facility for treatment. FTSI will be responsible for placement of dosimeters and reading of dosimeters before allowing the product to be released. FTSI uses two dosimetry systems Harwell PMMA dosimeters and Alanine dosimeters.

    How should our company specify (document) a sterility specification?

    FTSI will provide your company with a Certificate of Irradiation after each irradiation run that includes the dose and the lot numbers. The laboratory you use for validation can provide extensive documentation of your validation inclusive of sterilization.
    Sterility specification can be documented like you would document any other procedure in your company.

    Does your company need to monitor/track bioburden in products to compliment sterilization systems? What frequency?

    Dose audits do need to be performed on a quarterly interval. According to ISO 11137-1:2006 section A.12.1.3.1 “Historically, a three month time interval has been used to detect seasonal variations in bioburden.”

    How does your company validate its packaging? Packaging question example: “Will our current bag heat-seal systems be adequate for sterility shelf-life (stability)? Is there a specification as to how much seal force we require prior to burst.”

    Your company would validate packaging according to; ISO 11607-1:2006:Packaging for terminally sterilized medical devices — Part 1: Requirements for materials, sterile barrier systems and packaging systems and ISO 11607-2:2006:Packaging for terminally sterilized medical devices — Part 2: Validation requirements for forming, sealing and assembly processes

    The specification as to how much seal force is required prior to burst is greater than 1 lb.

    Please see attached links for a detailed explanation of some packaging tests: