Medical Device Sterility

The sterility of a medical device is often seen as a given by the user – but achieving and maintaining that sterility requires considerable thought, as a visit to Isotron’s laboratories, near Swindon, reveals

Isotron can assist with compliance to ISO 11137, offer guidance on testing methodologies, and provide environmental monitoring and training in hygiene and aseptic techniques

The sterility of a medical device is often seen as a given by the user – but achieving and maintaining that sterility requires considerable thought, as a visit to Isotron’s laboratories, near Swindon, reveals

Today, a large number of people rely on medical devices of some sort as part of their healthcare treatment. It may be something as simple as a dental implant or an MRSA test kit, or as complex as a pacemaker. More often than not, the patient simply assumes that whatever the device is, it will be safe and free of any harmful contamination i.e. sterile.

But that assumption relies on the manufacturer of the device following the relevant regulations. For example, in Europe that would be the EC Medical Devices Directives. These require manufacturers to ensure that their devices are safe and fit for their intended purpose before they are CE marked and placed on the market in any EU member state, and that they will continue to be supplied in a sterile form thereafter.

In the majority of cases this is what happens, but a look at the recent MHRA statistics for medical device recalls in the UK shows that it is not always the case and the incidence of non-compliance is increasing. In 2008, for example, the MHRA received 3.1% more adverse incident reports than in the previous year. The 8,902 total for 2008 also represented an increase of 41% over the 6,298 reports received 10 years earlier.

As a result of MHRA investigations in 2008, 88 Medical Device Alerts were issued, 96 notifications were shared with Competent Authorities in EU member states, and 568 manufacturer’s Field Safety Corrective Actions and 250 other manufacturer’s field actions were undertaken.

In the US, where the FDA is responsible for monitoring medical devices, the authority’s website shows that the number of medical device recalls rose from 18 in 2006 to 31 in 2009, and 24 recalls have been requested already by July 2010 – only halfway through the year.

The increase in recalls and corrective actions can be attributed to various factors: increased pressure on health practitioners to report device failures or adverse reactions; an increase in the number of devices being developed and placed on the market; and growing strictness on the part of the authorities regulating the market, to name but a few. Whatever the cause, the figures outline the need for manufacturers to ensure their devices are compliant before putting them on the market and that they remain compliant thereafter.

This is where the services of companies such as Isotron play an increasingly important role. The company, part of the Synergy Health Group, has been offering sterilisation services for single-use medical devices and other products for more than 30 years. But with demand increasing and regulation getting stricter, the company has recently made a significant investment in its facilities and has broadened the scope of the services it offers.

Contamination control

Isotron specialises in microbial contamin-ation control and polymer modification based on three technologies: Gamma radiation, ethylene oxide and acceleration beams (electron and ion) radiation. Some 65% of the company’s business is carried out for the medical and pharmaceutical sectors, with the remaining 35% consisting mainly of irradiation of polymers to enhance product strength.

The company has two labs in the UK – one at South Marston, near Swindon and one in Thorne, near Doncaster. At South Marston, the company has just finished expanding and refurbishing the lab, adding a second cleanroom and doubling the capacity for bioburden testing.

Looking through the corridor window into the new cleanroom facilities showing the testing performed under fume hoods and positive pressure airflow

The company can test a wide variety of products ranging from small dental fillings through to orthopaedic implants, surgical procedure packs or disinfectant sprays, to some of the larger pharmaceutical filling devices.

Isotron works with both big and small companies that, for various reasons, do not have in-house resources available for microbiological testing or the experience of testing method development, dose setting validation or dose audits.

“Our lab is all about ensuring compliance,” says Jenni Hollinsworth, Isotron’s UK marketing communications manager. “We work to ISO 11137, which covers the sterilisation of healthcare products via radiation, and ISO 11135, which specifies the requirements for the development, validation and routine control of an ethylene oxide sterilisation process for medical devices.

“The transition period for the ISO changes that took place in 2006 is now over and notified bodies are getting stricter with compliance,” she says.

“Some customers are aware of these requirements and others are not. Some of the smaller companies, for example, need a lot of support in achieving compliance.”

Every device is different and it is not unheard of for clients to arrive at the labs with newly developed but finished products, not having ever considered how they will make them sterile, says Hollinsworth.

“There is a common misconception that all you have to do is put a device through a sterilisation process and it will satisfy the authorities.

“Over the past 10 years the standards have changed. It used to be assumed that a 25kGy dose of radiation was enough to sterilise a device, but that was then. You can no longer just assume that a 25kGy dose is enough. Now companies need to have documented evidence that the device is sterile and has gone through a sterilising process.

“Today, you have to look at the type of contamination likely to be present and calculate the dosage needed for that particular device. Then a regime for regular testing needs to be in place to check compliance.”

With many of the new combination products – involving a medical delivery device and a drug – the company can help in determining the critical dose for sterilising the device without destroying the drug.

Critical changes

“A lot of our work involves making clients aware of what sort of things can have an impact on the sterility of their device,” says laboratory manager Susan Finlay-Woods. For example, changing a component, or even a change in the supplier of a component, can have a dramatic effect. Likewise, a change in the packaging or any change in the manufacturing process or amount of manual handling can also give rise to non-compliant results.

“The authorities want to see consistently low bioburden. They want confidence from a risk point of view that the device is sterile,” Finlay-Woods explains.

Another misconception is the timelines involved in testing. For example, to complete a sterility test involves 14 days of actual test time with some of the studies taking up to eight weeks, explains Hollinsworth. “Some elements have fixed timelines, which cannot be reduced.”

Isotron does, however, offer a fast track system for certain tests for companies who are working to tight timelines, in order to meet regulatory compliance or a product launch deadline, where work must be carried out to a specified time.

The recent rebuild of the facilities was carried out over a period of 12 months, in order to avoid any interruption of the business. It has enabled the company to increase product throughput. Finlay-Woods comments: “Changing the flow of products has made the process and sampling much more efficient.”

The company now has two cleanrooms, one of which is a Class ISO 7 cleanroom. Both rooms are under positive pressure and new bespoke product transfer hatches have been installed to help with product flow.

Testing is performed under fume hoods and positive pressure airflow

The company uses a corrective action, preventative action (CAPA) system to communicate with customers. In addition, goods are booked in at one end of the facility and can be tracked throughout the whole process via unique barcode identification.

Not only does the lab carry out bioburden determination and validation, as well as dose setting validation, it can also offer cleanroom environmental monitoring services as an extension of the manufacturing process. For this, Isotron supplies the settle plates, ready to place in the client’s cleanroom, and then carries out the required tests on their return.

Teaching compliance

Education is an important factor in helping Isotron’s clients reach compliance. The company has recently collaborated with a third party, High Edge Consulting, to offer services that help medical device manufacturers understand and comply with the relevant national and international standards and European Directives.

Isotron has also begun plans to increase the frequency of education days within the UK for clients to learn about the legislation and sterilisation methods and hear presentations from other device producers on how they have dealt with sterilisation issues.

A medical device requires a lot more thought to produce than the average user would imagine. The key to making the process easier, says Hollinsworth, is for developers to get a sterilisation company on board as early as possible in the development stage, to ensure components can be sterilised effectively and device registration goes smoothly.

In terms of continued compliance, Finlay–Woods concludes: “It all comes down to having a consistent and controlled manufacturing process.”

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