Required by ISO 14971, the risk acceptability matrix is the manufacturer's policy on how risk levels translate into action. It must be defined before risk evaluation and applied consistently across the risk management file. The matrix usually combines severity levels with probability levels and marks regions as acceptable, needing further reduction or unacceptable. ISO 14971:2019 requires the policy for establishing criteria to be set by top management and based on applicable standards, the state of the art and stakeholder concerns. Note that the EU MDR requires risks to be reduced as far as possible, which affects how a matrix's acceptable region is used for EU devices.

Why it matters

Notified Bodies frequently challenge inconsistent or unjustified matrices; aligning to ISO/TR 24971 examples is a defensible starting point.

Common pitfalls

•Failing to define the risk acceptability matrix before conducting risk evaluation can lead to biased assessments and non-compliance with ISO 14971.
•Inconsistently applying the risk acceptability criteria across different hazards or use scenarios will result in a non-compliant risk management file.
•Defining overly aggressive or overly conservative risk acceptability criteria without justification can lead to regulatory scrutiny or an unmarketable device.
•Not documenting the rationale for the chosen risk acceptability criteria is a common audit finding.
•Using a generic risk matrix without tailoring it to the specific device and its intended use is a significant oversight.

Sources

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Common comparison patterns

Regulatory pathway choice - 510(k) vs PMA, 510(k) vs De Novo, Abbreviated vs Special 510(k).
Quality systems - QSR vs ISO 13485, QMSR vs QSR.
Software classification - SaMD vs SiMD, Locked vs adaptive AI.
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MedTech Terms is a vendor-neutral community resource sponsored by Blue Goat Cyber. Definitions are written for educational use and are not legal or regulatory advice.