Aspen Medical Risk Consulting
Everyone
is Talking
about Risk
Assessing whether the Benefit of a medical product outweighs the Risk is a key metric of quality healthcare; e.g., both the United States (via the Code of Federal Regulations) and the European Union (via the Medical Device Regulations) require every medical product to show that its Benefits outweigh its Risks.
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Unfortunately, the state-of-the-art in assessing Benefit-Risk (aBR) is that there are no accepted method to determine whether Benefit or Risk is greater. Per section 7.4.1 of ISO / TR 24971, “The decision as to whether risks are outweighed by benefits is essentially a matter of judgment by experienced and knowledgeable individuals”.
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This method of aBR establishes a single structured framework that:
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Works for devices, drugs, biologics, combination products, and clinical trials,
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Sets new, higher standards for objectivity and transparency,
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Can simultaneously analyze large numbers of Benefits and Risks, avoiding most methods' requirement to consider only a few most-important factors,
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Avoids the trap of accumulating risk by assigning numbers and summing (per section 8.1 of ISO 14971, "The evaluation of overall residual risk . . . cannot be achieved by adding all individual risks numerically." Instead, both Risk and Benefit are accumulated as elements in a set.
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The process of concluding whether Benefit or Risk is larger is self- documenting, facilitating a considered review of the analysis steps leading to a conclusion.
In the 1990s, the United States' Food and Drug Administration (FDA) has been encouraging companies to use 'least burdensome' methods to document product quality, including making 'risk based' decisions to effectively allocate resources where they are needed the most. While industry and regulators have generally struggled with how to implement a 'risk based' philosophy, one area that has received broad industry support is using Risk to establish test sample sizes.
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While 'risk based sample size' procedures have multiplied, there remains a consistent problem with most company's procedures: Sample size is nearly always established based on only Severity or only Probability. Since, per ISO 14971, Risk is a combination of both Severity and Probability, all the procedures that use only Severity or Probability to establish sample size are not 'risk based'.
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Sample sizes based on Probability have the indefensible problem that, if a fatal failure and an apperance failure both occur at the same rate, then they are both tested with the same sample size. In reality, the fatal failure needs to be characterized in testing far more carefully than an appearance issue, so testing for a fatal failure requires a greater number of samples than an appearance failure. But a Probability-based sample plan ignores this critical factor.
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Sample sizes based on Severity alone have a similar, indefensible problem. If a frequenly occurring and a rarely occurring risk have the same severity, then they are both tested with the same sample size. In reality, frequently occuring failures can be detected with quite small sample sizes and extremely rare failures require greater numbers of samples. But a Severity-based sample plan ignores this critical factor.
This procedure not only uses solid statistical methodologies to establish statistically-significant sample sizes, the reliability of these samples sizes are truly 'risk based' because the method considers both Severity and Probability when establishing reliability.
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Acceptable Risk and the role of International Safety Standards (Click on the above image to download)
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