Risk Analysis Terminology Definitions

Thank you for your interest in risk analysis terminology definitions.

aFMEA (Application FMEA) - An FMEA that  focuses exclusively on user failures, both intentional and unintentional. Use the instructions for use (IFU) as a source material just as a dFMEA uses the bill of materials.

As Low as Reasonably Practical (ALARP) - The risk level that is greater than broadly acceptable, but less than unacceptable. Risks in this category must continue to be mitigated until the residual risk level reaches BA or further mitigation is impractical, whichever comes first.

Broadly Acceptable (BA) - The risk level that is low enough, based on current standards, such that no further mitigation is necessary.

Cause (contributing factor) - The proximate, or final, cause of a hazard or failure mode. The root cause or other contributing factors can be added as well.

Control (mitigation control) - Any means added to the design or manufacturing process that reduces the risk by reducing the severity, occurrence, or detection rankings. Severity usually cannot be reduced, except by some design changes.

Detection - Generally used only in pFMEAs, a rating that indicates the ability of the process to detect a manufacturing defect after it has occurred. This rating is typically improved by adding tests and inspections to the process. Although called detection, lower values indicate better detectability of defects than higher ones. A more accurate nomenclature would be non-detection, and this is the best way to think of it when working on a pFMEA.

dFMEA Design FMEA) - An FMEA that  focuses exclusively on the design, to the exclusion of the manufacturing process. A dFMEA assumes that there are no manufacturing defects present.

Effect - The effect is final manifestation of a failure, such as "incorrect value displayed" or "artery punctured." It is not the final outcome, such as death, serious injury, etc. This is the purpose of the severity rating.

Failure Mode - The failure mode is how a part fails to meet its design intent. A failure mode can be a part or joint breaking that is not supposed to break, or it could be a part wearing out sooner than specified.

Failure Modes and Effects (Criticality) Analysis (FMEA, FMECA) - An FMEA is a deductive risk analysis method. The FMEA uses a bottom-up approach to analyze the risks associated with component failures in a device that has been designed using a bottom-up approach. The device is reviewed part by part and assembly by assembly. Each potential failure mode is ranked for the probability that it will occur and the severity of the final outcome.

Harm - The undesirable final manifestation (effect) that occurs as a result of a hazardous situation. It is not the final outcome, such as death, serious injury, reversible injury, etc. This is the purpose of the severity rating.

Hazard - A condition, such as a failure, which could lead to a hazardous situation.  An exposed electrical cord is a hazard. Touching it is the hazardous situation.

Hazard Analysis (HA) - HA is an inductive risk analysis method. HA uses a top=down approach to analyze the risks associated with a class of device prior to the final design being started using a top-down approach. The device is reviewed by categories of hazards. Each potential hazard is ranked for the probability that it will occur, the possibly lower probability that harm will ensue, and the severity of the final outcome when harm does occur.

Hazardous Situation - The circumstance in which the hazard causes harm to occur. An exposed electrical cord is a hazard. Touching it is the hazardous situation, which causes an electric shock (the harm) to occur.

Occurrence (probability of occurrence) - The ranking of the likelihood that a failure mode, hazard, or hazardous situation will occur.

pFMEA (Process FMEA) - An FMEA that  focuses exclusively on the manufacturing process, to the exclusion of the design. A pFMEA assumes that the device has been designed as intended and contains no design defects.

Mitigation - The addition of controls to reduce the residual risk.

Residual Risk - The re-evaluated risk (BA, ALARP, or UA) of a single hazard or failure mode with the current number of controls for that hazard or failure mode in place. The risk level is determined from a table that defines the three risk zones as a function of the severity and occurrence rankings.

Risk (inherent risk) - The initial risk (BA, ALARP, or UA) of a single hazard or failure mode before any controls for that hazard or failure mode are put in place. The risk level is determined from a table that defines the three risk zones as a function of the severity and occurrence rankings.

Risk Priority Number (RPN) - In older FMEA formats, now falling out of favor for medical devices, the numerical product of the severity, occurrence, and detection values. A cutoff RPN value is used as the basis for risk acceptability levels, instead of a table.

Severity - A ranking of the most likely seriousness of the final outcome of a failure mode or hazardous situation. Examples include death, serious injury, reversible injury, etc.

Unacceptable (UA) - The risk level that is high enough to require sufficient mitigation to bring the residual risk level at least into the ALARP region.

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