FMEA rankings vs Hazard Analysis Rankings


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This is just a semantic issue. You're running into confusion simply because you're using "severity" to refer to two different concepts. They aren't necessarily incompatible, but they can easily be confused.

You have 14971-style medical "Severity of Harm". This is the ultimate actual harm to a patient, user or the environment. This is not optional, and it will always appear somewhere in your medical device risk management process.

Next, you have effects as identified by an FMEA - which you happen to be categorizing by the type of effect the failure has and how much it will disrupt the system. You've also called this categorizing "Severity", but it doesn't necessarily depend on harm to the patient. This one is not mandatory to comply with 14971 - in a real sense, it is just a tool you are using to prioritise or sort things somehow.

It's okay to have both of these, but I would strongly suggest you adjust your language to make the intent clear - otherwise you will absolutely have confusion and errors. In a medical device context, it is not okay to neglect a failure just because it is "small" - what counts is the type of harm that could occur.

If you want in your FMEA to categorise by effect on the system, I would recommend literally using that language. Rename the column to "Effect on System" and use words rather than numbers. It will be functionally identical, but make it abundantly clear that any evaluation for 14971 acceptability is done at a different level. Only use the word "Severity" for one thing - and if I were you, I'd pick the one that's actually mandatory for medical device risk management.


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(checks to make the thread is in the medical device forum)
The highest priority should be those things that are safety related functions, next would be necessary functions (i.e. failure to power up doesn't create a hazard for non-emergent therapies), then the 'nice to haves' as the lowest priority. Yes if the product doesn't work its a big deal to the business, but not as big as a safety issue.

Not at all true of course, because of that pesky Essential Performance issue, as it relates to Risk Management of medical devices.


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(checks to make the thread is in the medical device forum)

Not at all true of course, because of that pesky Essential Performance issue, as it relates to Risk Management of medical devices.

Yes true.
Essential Performance requires a safety impact and thus should be scored high. Necessary function is not equal to Essential Performance for non-emergent therapies and should not be scored as high as anything creating a safety concern. Guessing you were interpreting necessary function as Essential Performance.


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How is "Necessary Function" defined?
I think they are referring to intended use, something which gets verified during design validations irrespective of class II/III medical device.
(I skipped class I because Design Control is waived per CFR820.30, expect small subset of class I)


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When it comes to "important" functions as a group in medical devices, it's better not to start introducing non-standard terminology. Be as specific as you can using standard terminology. If you introduce in-house terms, have them clearly defined by relationship to standard terms (and try not to use them on forums)

If you want to look at functions that are needed to meet your intended use, then talk about functions needed to meet intended use.
If you want to look at the level of loss of clinical function that could present an unacceptable risk, then talk about essential performance.
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