Descriptions and Definitions of Quality Terms, Tools and Techniques

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Corrective and Preventive Action (CAPA)

There are effectively two basic ways of addressing quality problems: corrective and preventive.

Corrective action

Corrective action means correcting problems which have been discovered.

The basic corrective method is first to test or otherwise assess or audit the item after it has been completed. This provides the discovery process, after which the corrective action may take place.

The type of testing depends on the item being assessed. For a physical product this includes physical testing, which may be destructive. For documents such as plans assessment may be against checklists and templates. For large numbers or where testing is destructive, sampling may be used.

Testing starts at the planning and design stage, where the design includes consideration of how the items will be tested or assessed.

Corrective action may include:

• Rejection of an individual item or an entire batch.
• Rework to fix the problems found (short-term fix).
• Recovery and compensation of customers who experience the problem.
• Preventive action to prevent problems recurring (long-term fix).

The cost of corrective action includes:

• The cost of testing, including time for planning and preparation.
• The cost of testing equipment.
• The cost of items damaged by the testing process.
• The later cost incurred when faulty items are not detected during test.
• The opportunity cost of things not done due to the time and spend on corrective action.

Ideally, corrective action takes place immediately after an action is completed, (this is known as 'source inspection') rather than incurring the additional cost of discovering the problem down the line.

Corrective action may need to be written up in a Corrective Action Report (CAR) and/or Non-Conformance Report (NCR). Such reports are used to ensure corrective action is done properly, that metrics are collected and that appropriate preventive action is undertaken.

Preventive action

Preventive action means acting to prevent problems from ever occurring (or reducing the probability of occurrence).

The basic preventive method is design. Products, processes and systems are structured such that problems cannot appear. This may include methods such as Poka yoke and utilize checklists to ensure actions are completed. For human processes it may include aspects of psychology and work study to simplify and make work easier.

The cost of preventive action includes:

• Additional cost during design
• Additional cost of preventive action in practice

Preventive action does not replace corrective action, but it should significantly reduce the number of defects round and the attendant costs.

CAPA

Together, these are known as Corrective and Preventive Action (CAPA) and may be identified through a standard process such as:

1. Identification: Defining the problem
2. Evaluation: Appraisal of risks
3. Investigation: Planning research of the problem
4. Analysis: Deep assessment of causes
5. Action plan: Listing actions to complete, including training
6. Implementation: Implementing the plan
7. Follow up: Checking that it works as intended

CAPA programmes of work are common across business contexts and seek to address this issue in a systemic way, providing a consistent approach that has a significant effect on overall quality.

CAPA work may be triggered by such as:

• Customer complaints
• Product failure
• Process failure
• Input inspection
• Audit/assessment observations
• Grass roots observations by employees

See also:

Sampling, Poka yoke, Source inspection

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