How to select and help validate the best sterilization method?

The FDA eSTAR includes a list of eight different options for a sterilization method, but how do you select the best method and validate it?

Sterilization Method Selection 1024x576 How to select and help validate the best sterilization method?

What is Sterile Packaging Day?

The Sterilization Packaging Manufacturers Council (SPMC) founded Sterile Packaging Day in 2021 to recognize and thank all of the companies in the supply chain who work together to deliver innovative, safe, and sterilized devices to provide excellence in patient care. Sterile Packaging Day is February 8, 2023, and this year’s celebration theme is “Designed to Protect.” SPMC provides four tips for celebrating Sterile Packaging Day:

  1. Donate blood (use this link for an appointment) on February 8, 2023, at MD&M West in Anaheim
  2. Recognize and thank an esteemed packaging professional with whom you collaborate for success
  3. Support the next generation of packaging engineers (FPA Student Design Challenge)
  4. Tell us in one word what “Designed to Protect” means to you (Rob chose “Lifesaving”)

Thank you to Jan Gates!

How to select the best sterilization method

Several factors determine the best sterilization method to use for your device. The first factor is whether your device will be delivered sterile or will the end user sterilize the device. If the end user is responsible for sterilizing the device, the most common methods used by hospitals are:

  1. steam sterilization
  2. hydrogen peroxide sterilization
  3. EO sterilization

The popularity of the third method is declining due to environmental restrictions on hazardous emissions from the ethylene oxide sterilization process. Hydrogen peroxide is gaining popularity because it can be used for heat-sensitive materials, and hydrogen peroxide vapor reacts with moisture to form a harmless aqueous solution. Steam is the most common sterilization method used by doctors, dentists, and hospitals because steam sterilizers are relatively inexpensive, and no hazardous chemicals are required.

The second factor to consider when selecting a sterilization method is whether there are any heat-sensitive components. Plastics will melt and degrade in dry heat sterilization cycles, and some plastics cannot withstand the temperature of a steam sterilizer. Therefore, if your device is constructed from plastics for cost reduction, weight, magnetic resonance (MR) compatibility, or other reasons, you may need to use a sterilization method with a lower temperature process.

The third factor to consider when selecting a sterilization method is whether any long, narrow tubes require sterilization. These design features are difficult to sterilize for any vapor-based sterilization process, such as steam, hydrogen peroxide, or ethylene oxide. There are a few process control strategies that can be used to sterilize with gas:

  • use of an extreme vacuum to improve penetration of sterilant gas
  • ensuring that the device and packaging materials are dry
  • use of longer cycles with more sterilant gas
  • use of internal biological indicators at the most difficult sterilization location

The fourth factor to consider when selecting a sterilization method is whether the device includes a liquid. A liquid cannot be sterilized with hydrogen peroxide, ethylene oxide, or dry heat. In some cases, the liquid may be a sterilant (i.e., ISO 14160:2021 for liquid chemical sterilizing agents). There are three popular solutions for the sterilization of a device that includes liquid:

  1. steam sterilization–assuming the liquid doesn’t contain components that are heat sensitive (e.g., proteins)
  2. filter sterilization–usually combined with aseptic filling and pre-sterilizing containers)
  3. radiation sterilization with eBeam or Gamma

eBeam and Gamma are also used for sterilizing products where cross-linkage of ultra-high molecular weight polyethylene (UHMWPE) is desired, or it is impossible for a gas sterilant to penetrate all areas of a device.

What are the applicable sterilization validation standards for each sterilization method?

As shown in the FDA eSTAR screen capture above, eight possible sterilization methods can be selected for sterilizing a medical device in a 510k or De Novo submission. Each sterilization method has a different applicable standard that should be used to validate the sterilization process, but in all cases, the sterilization process must result in a sterility assurance level (SAL) of 10-6.

The FDA feels that the Established A (Est A) methods of sterilization have a long history of safe and effective use, while the FDA has not recognized a dedicated consensus standard for the Established B (Est B) sterilization methods. However, there are examples of devices that have received FDA 510k clearance using each of the non-traditional sterilization methods (i.e., Est B methods). Manufacturers will generally adapt existing international standards for sterilization validation to validate the non-traditional methods. There is published information on the development, validation, and routine control for these non-traditional sterilization processes.

Links to each of the recognized standards are provided below:

  1. Steam (Moist Heat) (Est A) – ISO 17665-1:2006, Sterilization of health care products — Moist heat — Part 1: Requirements for the development, validation, and routine control of a sterilization process for medical devices
  2. Ethylene Oxide (EO, EtO) (Est A) – ISO 11135:2014, Sterilization of health care products – Ethylene oxide – Requirements for development, validation and routine control of a sterilization process for medical devices; and ISO 10993-7:2008, Biological evaluation of medical devices – Part 7: Ethylene oxide sterilization residuals
  3. Radiation (Est A) – ISO 11137-1:2006, Sterilization of health care products – Radiation – Part 1: Requirements for development, validation, and routine control of a sterilization process for medical devices; ISO 11137-2:2013, Sterilization of health care products – Radiation – Part 2: Establishing the sterilization dose
  4. Dry Heat (Est A) – ISO 20857:2010, Sterilization of health care products – Dry heat – Requirements for the development, validation and routine control of a sterilization process for medical devices
  5. Hydrogen Peroxide (Est B) – ISO 22441:2022, Sterilization of health care products — Low temperature vaporized hydrogen peroxide — Requirements for the development, validation and routine control of a sterilization process for medical devices (this standard is not recognized by the US FDA)
  6. Ozone (Est B) – this is a new method using Ozone gas, and the method of action is similar to EO and H2O2
  7. Flexible Bag Systems (Est B) – ISO 22441:2022 should be used for validation of flexible bag systems with hydrogen peroxide, but instead of validating the process with three half-cycles that are half the duration of the full-cycle, instead, you use three half-cycles that use half the volume of sterilant of a full-cycle; this method is used by Andersen Scientific for their EO Bag sterilizers.
  8. Novel Methods – ISO 14937:2009, Sterilization of health care products – General requirements for characterization of a sterilizing agent and the development, validation and routine control of a sterilization process for medical devices

When should you use a novel sterilization method?

Novel sterilization methods should only be used when none of the traditional (Est A) and non-traditional (Est B) sterilization methods will not work. For example, aseptic filling combined with filtration of liquids is a common strategy for pre-filled syringes if the liquid is sensitive to radiation sterilization. Sterilization with peracetic acid has been used for a long time, but the sterilization method has not gained widespread popularity. Peracetic acid can also be combined with hydrogen peroxide. There is also a low-temperature steam and formaldehyde validation standard (i.e., ISO 25424:2019). Sterilization with UV light is a process that is sometimes used where materials are sensitive to high temperatures and where all surfaces can be penetrated with UV light. Nitrogen dioxide was developed as a more environmentally friendly sterilant similar to ethylene oxide. X-Ray is a new type of radiation sterilization that is being developed as a high-speed alternative to Gamma and eBeam, but X-Ray sterilization also has the advantage of being able to control a narrower dose range than Gamma and eBeam processes.  

Consensus Standards for Sterilization Validation

There are also additional supporting standards that you will need for validation of your sterilization process. The following is a partial list of the standards you might consider:

  • ISO 11737-1:2018, Bioburden Testing for Aerobic Bacteria and Fungi
  • USP<51> Antimicrobial Effectiveness Test
    • Candida albicans (a yeast…yeasts are a form of fungus)
    • Aspergillus brasiliensis (a filamentous mold…also a fungus)
    • Escherichia coli (a bacterium…better known as “E. coli”)
    • Pseudomonas aeruginosa (a bacterium….very problematic industrially)
    • Staphylococcus aureus (a bacterium…better known as “Staph”
  • USP<61> Bioburden or Microbial Limits Test (Total Aerobic Microbial Count = TAMC; Total Yeast and Mold Count = TYMC)
  • USP<62> Objectionable Organisms or Pathogens Tests
  • USP<63> Mycoplasma Tests
  • USP<71> Bacteriostasis/Fungistasis (i.e., B/F) Sterility Tests
  • ISO 11138-1:2017, Sterilization of health care products – Biological Indicators – Part 1: General Requirements
  • ISO 111140-5:2017, Sterilization of health care products – Chemical indicators – Part 5: Class 2 indicators for Bowie and Dick air removal test sheets and packs
  • ISO 17664-1:2021, Processing of health care products – Information to be provided by the medical device manufacturer for the processing of medical devices – Part 1: Critical and semi-critical medical devices

Aging and Shelf-life Testing

The current standard for accelerated aging studies is ASTM F1980:2021 “Standard Guide for Accelerated Aging of Sterile Barrier Systems and Medical Devices has been revised and recently released to include medical devices.” Jan Gates explains that the “and” used to say “for.” The language was updated with more information on product humidity effects to go with the title. Jan was kind enough to write a Shelf-life Testing Protocol for us based on this new version of the standard. The protocol includes requirements for real-time and accelerated age testing of a product. If you need basic training on how to validate the shelf-life of your device, we have a webinar for sale on sterility and shelf-life. We also recorded an updated webinar on January 19, 2023, as part of the FDA eSTAR updates to our 510(k) Course.

Distribution Conditioning Tests & Packaging Performance Tests

There are also standards for distribution conditioning tests (i.e., ASTM D4169-22). Jan Gates was kind enough to write a 20-page Distribution Conditioning Shipping Qualification Protocol for Medical Device Academy based upon the ASTM standard. The protocol is available for purchase at the link above. Jan also wrote an 18-page Packaging Performance Testing Protocol for our customers in accordance with ISO 11607-1 and ISO 11607-2.

Where can you find a procedure for each sterilization method?

ISO 13485:2016, Clause 7.5.7 is specific to the “Particular requirements for validation of processes for sterilization and sterile barrier systems.” This clause includes the requirement to establish procedures for sterilization validation and validation of your sterile barrier systems. Even if your company uses a protocol and procedures established by a contract manufacturer, you still need to establish an internal procedure(s) to meet this requirement if you have sterile products. The following is a list of procedures sold by Medical Device Academy:

What is the process flow for contract sterilization?

Most device manufacturers do not sterilize their devices in-house. Instead, sterilization is outsourced to a contract sterilizer. The process flow diagram below is a hypothetical process flow diagram for a contract sterilization process. The only step not included in this process flow is the incubation of biological indicators because gamma and eBeam sterilization processes use dosimeters instead of biological indicators. The nature of biological indicators is also changing rapidly because manufacturers are developing “rapid test” biological indicators. In 2008 I worked extensively with self-contained biological indicators that eliminated the need to use an aseptic technique to transfer biological indicators into culture media. In addition, I complete an incubation reduction study to validate a shorter 48-hour incubation cycle instead of the typical 7-day sterility test. Terragene is one of the manufacturers developing next-generation technology for biological indicators that allows the results to be read within seconds instead of 48 hours. This next-generation technology also incorporates barcode readers and networked readers to ensure traceability to each biological indicator and reader.

Generic Sterilization Process Flow Diagram 731x1024 How to select and help validate the best sterilization method?

What information should serialized labels include for contract sterilizers?

In the “olden days” (c. 2005), I used to print out labels for each pallet that we shipped to the Isomedix facility in Northboro, MA. The label identified who the product was from and what we wanted Isomedix to do with the product (e.g., gamma sterilize at 25-40 kGy). At the time, we were just beginning to incorporate barcodes into on-demand labeling to facilitate traceability. 18 years later, companies are still stalling the implementation of on-demand barcoded labels. Almost every shipping dock has a barcode reader, and the technology is inexpensive. Therefore, you should consider creating a template for on-demand barcoded labels with all the information listed below. This will reduce the risk of errors by the contract sterilizer and enable you to identify when a mistake was made quickly. Contract sterilizers should also demand this information on product labeling as an added risk control. All biological indicators and dosimeters are labeled with UDI barcodes now. Therefore, contract sterilizers should be able to create robust process controls that ensure traceability between barcodes on your labeled product with barcodes on the biological indicator or dosimeter.

2 Customer Prints Serialized Labels 1024x816 How to select and help validate the best sterilization method?

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Performance Qualification (PQ) for EO Sterilization Validation

The article explains requirements for a performance qualification (PQ) of EO sterilization validation and how it is different from other PQ process validations.

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Mind your ps and qs 1024x291 Performance Qualification (PQ) for EO Sterilization Validation

Performance Qualification (PQ) – What is the difference between an IQ, OQ, and PQ?

When you are performing a process validation, the acronyms IQ, OQ, and PQ sometimes confuse. IQ is the installation qualification of the equipment used in your validated process. The purpose of the installation qualification is to make sure that your equipment was installed correctly–this includes calibration and connection to utilities. OQ is the operational qualification. The purpose of the operational qualification is to make sure that the equipment you are using is capable of operating over the range of parameters that you specify to make your product. The PQ is a performance qualification. The purpose of the performance qualification is to ensure that you can consistently make a product within specifications (i.e., repeatable).

Different Definitions for Operational Qualification (OQ)

The GHTF guidance document for process validation provides the following definition for an OQ: “Establishing by objective evidence process control limits and action levels which result in a product that meets all predetermined requirements.” ISO 11135-1:2014, the international standard for ethylene oxide (EO) sterilization validation, provides a slightly different definition for an OQ: “process of obtaining and documenting evidence that installed equipment operates within predetermined limits when used in accordance with its operational procedures.” The difference in these two definitions is essential because the OQ is typically performed by contract sterilizers and does not need to be repeated unless there is a significant change or maintenance to the sterilizer that requires repeating the OQ. In contrast, when you perform an OQ for packaging, the OQ is specific to the packaging materials you are going to be sealing. Therefore a new OQ is required whenever new packaging materials are developed. For EO sterilization, the analogous step of the validation process is called a microbial performance qualification (MPQ).

Performance Qualification (PQ) = MPQ + PPQ

A performance qualification (PQ) for ethylene oxide sterilization validation consists of two parts: 1) microbial performance qualification (MPQ), and 2) physical performance qualification (PPQ). The microbial performance qualification is intended to determine the minimum process parameters for the EO sterilizer sufficient to ensure product bioburden is killed. These parameters are referred to as the half-cycle because the full production cycle will be twice as long in duration. For example, a half-cycle consisting of 3 injections will correspond to an entire cycle of 6 injections.

What are fractional cycles?

Fractional cycles are typically shorter in duration than the duration of a half-cycle. The purpose of a fractional cycle is to demonstrate that external biological indicators (BIs) located outside of your product, but inside the sterilization load, are more challenging to kill than internal BIs. Fractional cycles are also be used to demonstrate that the product bioburden is less resistant than the internal BIs. To achieve both of these objectives, it is typical to perform two fractional cycles at different conditions to make 100% kill of internal BIs and partial external BI kill in one fractional cycle, and 100% kill of product bioburden but only partial kill of internal BIs in the other fractional cycle. When your goal is partial kill, you should also target more than one positive BI, because this reduces the likelihood that poor technique resulted in a BI positive from growth.

Microbial Performance Qualification (MPQ)

The microbial performance qualification (MPQ) typically consists of three half-cycles and one or more fractional cycles. 100% kill of external BIs is not required for the MPQ during a half-cycle–only the internal BIs must be 100% killed, but the external BIs are only useful if 100% kill of the external BIs is achieved in the full cycles. If you are re-validating the sterilization process, you are only required to complete one-half cycle and one fractional cycle. For re-validation, the fractional cycle is intended to achieve a 100% kill of product bioburden. Still, only partial kill of internal BIs to verify that the product bioburden remains less resistant to sterilization than the internal BIs. You are also required to perform bioburden measurements of non-sterile products for the initial MPQ and re-validation to demonstrate that bioburden can be adequately recovered from the product and measured.

Physical Performance Qualification (PPQ)

The physical performance qualification (PPQ) typically consists of three full cycles and measurement of EO residuals in accordance with ISO 10993-7:2008. If PPQ is performed during the MPQ, then it is only necessary to complete one full cycle–assuming the MPQ consists of at least three half-cycles. If you are performing a re-validation of the sterilization process, then you are required to complete three full cycles and measurement of EO residuals.

Repeatability, Reproducibility, Product Variability and Environmental Factors

Typically a performance qualification (PQ) is intended to verify that the same person can repeat the process multiple times, other people can reproduce the first person’s results and any variation product from lot to lot will not prevent the process from producing an acceptable product. Besides, any variation in environmental factors should be assessed during a PQ. In sterilization processes, however, the equipment is typically automated. Therefore, variation between operators is usually a non-issue. Also, sterilization lots typically consist of a large volume of products where multiple samples are tested for sterility. Therefore, performing three runs sufficiently challenges the repeatability and reproducibility of the sterilization process–including any product variability. The issue of environmental variations in heat and humidity is addressed by designing preconditioning cycles into the sterilization process. Sensors are included in each validation load to verify that the process specifications were achieved and maintained for temperature and humidity. Still, the sensors also help to identify the worst-case locations in a load to use for sampling and placement of BIs.

If you are interested in learning more about sterilization validation, please read our blog from last year on an evaluation of the need to re-validate your sterilization process, or you can watch our webinar on sterilization and shelf-life testing. You can also purchase our procedure for EO sterilization validation by clicking on the link below.

Purchase the EO Sterilization Validation Procedure (SYS-031) – $299

EO Sterilization Cycle 1 150x150 Performance Qualification (PQ) for EO Sterilization Validation
SYS-031 EO Sterilization Validation Procedure
This new procedure defines the requirements for ethylene oxide (EO) sterilization validation and revalidation which has been outsourced to a contract sterilizer.
Price: $299.00


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IFU validation is not a risk reduction – Deviation 7

This article describes how to perform IFU validation before commercialization and how to conduct post-market surveillance to ensure that your IFU continues to be suitable as your user population and patient population expand.

IFU Validation and PMS IFU validation is not a risk reduction   Deviation 7

Most companies create an IFU for a new product by plagiarism. They merely copy a competitor’s IFU and change the name. If a regulatory expert creates the IFU, the IFU will be nearly identical to the competitor IFU. However, if a marketing person creates the IFU, the IFU will explain how your product is different from the competitor’s product. Neither approach is practical.

Creating a risk-based IFU

EN ISO 14971:2012 identifies deviations between the ISO 14971:2007 international standard and the three EU Directives. However, deviation #7 is specific to labeling and instructions for use. Even if your product is not CE marked, you should be developing a risk-based approach to IFUs. The priority of risk controls is to eliminate and reduce risks by design, manufacture, and selection of materials. The second priority is to implement protective measures such as alarms to warn users of risks. The last priority for risk controls is to inform users of residual risks. The best practice is to utilize a risk traceability matrix to document each of the risk controls you implemented to eliminate and reduce the risks of hazards identified.

The EN version of ISO 14971 will not allow you to reduce risks quantitatively in your risk assessment for information provided to users about risks, because this type of risk control is not entirely effective. However, you are required to verify that each residual risk is disclosed to users in your IFU, and you must validate that your warnings, precautions, and contraindications are adequately identified such that users understand the residual risks. You are also required to determine any user training needed to ensure specified performance and safe use of your medical device in accordance with ISO 13485:2016, Clause 7.2.1d. Clause 7.2.2d) requires that your company ensure that user training is made available. Any user training you provide should also be validated for effectiveness.

When to perform IFU validation

Some companies ask physicians that helped them with product development review draft IFUs. However, these physicians are already familiar with your product, and your company, and they are highly skilled in the specific procedures your device will be used for. After your experts have made their final edits to your draft IFU, you now need a “fresh set of eyes.” The best approach is to validate the effectiveness of your IFU with potential users that don’t know you or your company. If your product requires animal performance testing or human clinical studies, you could use these studies to validate your IFU. However, I recommend conducting a simulated use study before conducting animal or human studies. Conducting a simulated use study before animal and human studies can prevent deviations from your documented protocols that were caused by the inadequate review of the IFUs.

Methods of IFU validation

The best method for validating your IFU is to perform a simulated use study or human factors study. The FDA published a human factors guidance document that can help you assess the risk of human factors and ergonomics. The FDA guidance requires that you identify your intended user population(s). For each individual population of users, you are required to have a minimum of 15 users for your study. If your product is not for specific indications, you may be able to select 15 users at a few sites randomly. However, if your device is intended for two different specialties, then you need 30 users–15 for each specialization.  I recommend recording a video of simulated use studies too. Videos identify small details that you might miss, and clips from the videos are useful in creating training videos for future users.

Gathering Post-Market Surveillance

Post-market surveillance is not just asking customers if they are satisfied. You need to continue to monitor adverse event databases, your complaint database, and any service records to determine if there are any new risks and to verify that the risks you identified were accurately estimated concerning severity and probability of occurrence of harm. Clinical studies and PMS are the only way you can gather data regarding the likelihood of occurrence of harm. When you design your post-market surveillance questions, make sure you include questions explicitly targeting the residual risks you identify in your IFU. You should also ask, “What indications do you use this device for. Specifically, please identify the intended diagnosis, treatment, and patient populations.” This wording is more effective than asking if a physician is using your product “off label.”

Revalidation of IFU after labeling changes

Changes to labeling and IFUs should always be considered design changes and may require revalidation. If the switch is in response to a complaint or CAPA, then you must revalidate the IFU and labeling to verify the effectiveness of your corrective action. Any validation should be documented, reviewed, and approved before implementation, and acceptance criteria should be determined ahead of time. Your acceptance criteria should be quantitative, so you can objectively determine if the change is valid or not. You might be able to copy your previous IFU validation protocol or simulated use protocol and simply repeat the validation precisely as you did before with new users. However, sometimes the reason why the IFU was not 100% effective in the past is that the risk you are addressing in the revised IFU was not evaluated adequately in the original simulated use protocol.

New webinar for risk-based IFU validation and PMS

If you want to learn more about using a risk-based approach to developing IFUs, validating IFUs, and performing post-market surveillance to monitor the effectiveness of your IFU, then please click on the webinar link below.

IFU Validation Webinar Button 300x62 IFU validation is not a risk reduction   Deviation 7

If you are interested in ISO 14971 training, we were conducting a risk management training webinar on October 19, 2018.

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Validating Bioburden Limits

This article explains the process for setting and validating bioburden limits, and you will learn when investigations are needed. 

Last week, I was in Europe reviewing product specifications with a potential contract manufacturer for a medical device implant. Due to the raw materials that the contract manufacturer currently is using for a similar product, bioburden levels are higher than we can accept. The company uses an ISO Class 7 cleanroom for assembly and packaging, which is clean enough for these implants, but the molded components used for the assembly are not clean enough.

Validating Bioburden Limits Validating Bioburden Limits

The average bioburden is 220 CFU/device (i.e., colony-forming units/device), and the maximum observed bioburden exceeded 500 CFU/device. We want to use a lower dose range of gamma radiation to prevent the deterioration of bioabsorbable plastics, but a lower dose range requires that the average bioburden never exceed 100 CFU/device.

There are quite a few Clauses in ISO 13485 that differ from ISO 9001. One example is Clause 6.4–Work Environment. Subsection 6.4(b) states, “If work environment conditions can have an adverse effect on product quality, the organization shall establish documented requirements for the work environment conditions and documented procedures or work instructions to monitor and control these work environment conditions.” This is the applicable clause of ISO 13485 related to setting bioburden limits. Unfortunately, this vague requirement does not explain how to establish or validate bioburden limits.

Rule of Thumb for Setting Limits

One of my microbiologist friends recommends using the following “rule of thumb”: +2 sigma for alert limits and +3 sigma for action limits. This rule of thumb assumes that you are performing data analysis of bioburden and that you have calculated a “sigma” value for the standard deviation. There are a few problems with the “rule of thumb” approach.

First, this method assumes a normal distribution and a controlled process–which bioburden seldom is. Second, the cleanliness you need for your product and the cleanliness your controlled environment is capable of are not always appropriately matched. In my example, we need the finished device to have a bioburden of <100 CFU/device before gamma sterilization. Molded parts are essentially bioburden free due to the hot temperatures of the parts ejected from the mold. Unfortunately, molded components attract dust like a magnet. Therefore, how you handle and store molded parts is important to the bioburden of the molded parts.

Which factors affect bioburden?

For this example, we have three aspects critical to the final bioburden limit of the finished medical devices.

  1. How are the molded parts handled and stored?
  2. Are molded parts cleaned before assembly?
  3. What is the cleanliness of the work environment where the device is assembled?

The cleanliness of the molding environment matters, but parts can fall into a container that keeps the parts clean. It also matters how molding machine operators handle the parts. Gloves should be used, and typically the container the parts are in will be placed in an outer bag for storage. It is possible to clean molded parts with ultrasonic cleaning before assembly, but if the parts are kept clean after molding, this is unnecessary.

For your assembly operation, you need an environment with suitable cleanliness. Sometimes a controlled environment is sufficient. Other times a certified cleanroom is more appropriate. In either case, it is important to control the bioburden in the assembly area to a level that meets the needs of the most critical product assembled in that area. Cleanroom procedures, the design of the cleanroom, and your cleaning/sterilization processes should match the needs of the product. Fortunately, cleanroom procedures and bioburden limits for cleanrooms are well established in ISO 14644-1 (e.g., for an ISO Class 7 cleanroom, particles ≥ 0.5 microns must be fewer than 352,000). If you have devices of different types in the same manufacturing area, you must plan according to the most critical needs.

Validating Bioburden Limits

After establishing your bioburden limits, you need to validate these limits. Once again, cleanroom validation has established ISO Standards to follow. The more challenging validation is a validation of the bioburden of parts and the final assembly. It’s important to validate the component levels first to reduce the variability of inputs to the final assembly process. Typically the first step is to perform data analysis of other molded parts produced in the same molding area by the same operators. If this data meets your needs for cleanliness, then further measures for controlling bioburden may not be needed. However, if you need to reduce bioburden (i.e., bioburden failure), you might consider measuring parts at critical control points. The goal is to identify where the bioburden is being introduced. This analysis is typical of the type of root cause investigation performed when bioburden increases for unexplained reasons.

Once the sources of bioburden are identified and quantified, process controls should be implemented to reduce bioburden. Gloves, double-bagging of product, and keeping containers covered during the molding operation are typical risk controls that may be implemented. To validate the effectiveness of these measures, you should write a bioburden validation protocol that evaluates each of the following aspects:

  1. lot variability of component bioburden
  2. operator variability for assembly
  3. variability in the cleanliness of the assembly area
  4. number of operators in the assembly area
  5. duration of the manufacturing lots

After you have validated the bioburden limits for the components, then the same process should be conducted for the final assembly of the product. A sampling of bioburden after transfer to the assembly area and before assembly begins should be done. This is important because often, improper storage of components and/or failure to remove and clean outer packaging will contaminate the parts and your assembly area.

process validation webinar Validating Bioburden LimitsIf you are interested in learning more about process validation, please download the process validation webinar. We also published a blog on sterilization and shelf-life validation for 510k submissions.

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Medical Device Validation Document Resources

This blog provides a list of medical device validation resources and explains how to create your resource list.

medical device academy valdiation resources Medical Device Validation Document Resources

The first step to understanding how to conduct successful validations are always to read and re-read the requirements of the documents below:

  • 21 CFR 820.30(g)
  • 21 CFR 820.75
  • ISO 13485, Clause 7.3
  • ISO 13485, Clause 7.5.2

Unfortunately, we sometimes need to consult a reference guide that explains aspects of the requirements.

Max Sherman ( is finishing a new handbook on design and process validation that will be published through RAPS. The following is a list of resources for the process and design validation that I am submitting for publication in the book. Many of these resources are free, and these are the resources I use to learn and teach principles of validation.

  1. GHTF/SG3/N99-10:2004 – Process Validation Guidance (
  2. ISO 14969 – ISO Guidance document for ISO 13485 (
  3. 13485 Plus – CSA Guidance document for ISO 13485 (
  4. AAMI The Quality System Compendium: Bundled Set of Textbook & CD (
  5. The preamble to the QSR (
  6. ICH Q2: Validation of Analytical Procedures: Text and Methodology (
  7. FDA Guidance for Part 11: Electronic Records (
  8. FDA Guidance for Software Validation (
  9. FAQs about Implementation of IEC 62304:2006 (

In addition to these resources, you may also need additional resources for design validation. Here are some examples of design validation resources I use in my design controls training “tool kit:”


As regulatory affairs professional, it is critical to maintain a list of the most current standards and an organized list of links to those standards. I used to keep a list of favorites in my web browser for this purpose, but my database now exceeds the utility of “favorites.” Now, I use my webpage for this purpose. You can do this yourself by creating a free WordPress blog, and having one of the webpages to the blog be specifically to maintain a list of applicable Standards. Here’s a link to my webpage that I share:


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