Estimating Risk - where to stop when determining potential harm

[Tidge]

I have used systems that allowed for ad hoc risk reviews as well. Apply some critical thinking of course.

 

[d_addams]

I have a question along similar lines, close enough that I think it can fit within this same thread.

What if you have a hazard and hazardous situation that has managed to cause a harm (cut) of a higher severity than you thought would be possible - from a Severity 1 within the assessment to a severity 3.
So now there is evidence of both severities occurring, with the severity 3 occurring at a less than 1 in a million uses, but still has occurred.

As there is now evidence of occurrence, every part of me is saying that this now needs to also be a part of the hazard analysis, so we have two cut harms listed with different severities. There are unlikely to be any changes in controls as a result of this, however it may now be necessary to disclose the residual risk to users in the user manual.

But receiving questions of "do we really need to do that, for one occurrence in over 20 years"

Do we?

IMO this is the right answer. Your FMEA or FTA or Therapy Hazard Assessment (risks that arise without system failure/malfunction) should not attempt to estimate the occurrence of harm, they should assessment the frequency (or criticality) of the occurrence of the hazard (such as a cut or an infection). Then in your Risk Analysis for a given hazard (such as a cut or an infection) you now assess the frequency of the spectrum of harms resulting from the hazard. This is where you get to sum the occurrence of the hazards (P1s) from your design analyses (FMEA, FTA, THA, etc.) then for that hazard you can expect to see a spectrum of outcomes and you'll have different ratios of conversions to harms (P2s). This addresses the biggest short coming in how many people do Risk Management. They just stick with a singular (worst case) harm for a failure and either have everything cascading to worst case and getting no stratification in their design analysis or go with the most likely harm severity and don't adequately capture the potential for rare high severity outcomes in their Risk Analysis. Particularly when people use their FMEA as their Risk Analysis.

This allows for a complete picture of all of the harms that WILL occur in the patient population when prescribed this product/therapy. Given enough patients all kinds of odd things will happen. I'd prefer to not have to argue with a regulatory body that the event wasn't due to the product or procedure or that 'we get to stop at cut/infection and don't need to analyze any further'. I prefer to say this was an identified potential harm and is occurring within the expected rate.