· 8 min read
Developing and Improving Quality Management Systems
At NSF International, we work with companies on root cause analysis training and help companies improve their investigation systems and reports. The CAPA hierarchy is one of the most simple yet most effective tools in our toolbox.
In this article, we will look at:
- How you can make effectiveness checks meaningful.
- The CAPA hierarchy.
- What you can do to eliminate the possibility of error.
- An example project where we used these tools on a client site.
- Ways to replace the current process with a more reliable process.
- How to reduce mistakes.
- How to improve detection.
- Next steps that you can take.
Have you ever reviewed an investigation report and wondered whether the proposed corrective and preventive action (CAPA) would be effective?
Sometimes, we shrug our shoulders and say, “At least they put something in place.” We all know that the FDA expects us to include an effectiveness check, but do we have enough guidance to make these checks meaningful?
How To Make Effectiveness Checks Meaningful
NSF suggests that you consider these three questions:
- What will you measure?
- When will you measure it?
- What is your acceptance standard?
Here are two examples of how you can make your effectiveness checks meaningful:
- Three months after implementation of the CAPA, check for repeat incidents. If there are no incidents, close the CAPA. If there are repeat incidents, re-open the investigation.
- Ten batches after implementation, calculate the new average reject rate. The CAPA is successful if the reject rate is less than 1.5 percent. If the new reject rate is higher than 1.5 percent, re-open the investigation.
But are these requirements sufficient? Is there any way we can evaluate the CAPA before implementation? We will lose valuable time if we must wait three to six months for the answer. The regulatory risk increases as the clock keeps ticking.
The CAPA Hierarchy
We propose introducing a CAPA hierarchy that investigators can use to help them select an appropriate CAPA most likely to deliver the desired outcome. It can also be used by approvers. The CAPA hierarchy might even give investigators additional leverage to push back for a better solution or help them articulate weaknesses they saw in previous CAPAs. After all, some corrective actions ARE more effective than others.
Eliminating the Possibility of Error
Eliminate the possibility of error. This can be accomplished by eliminating the task. Here are some examples of how you can eliminate the possibility of errors:
- Eliminate mixing errors by purchasing pre-mixed materials.
- Eliminate recording errors by linking the measurement device to a printer.
Elimination can also be accomplished by a poka-yoke (an error-proof device). This concept is widespread in manufacturing, where a special fixture makes a part impossible to install incorrectly.
Example: IV Bags
NSF participated in an investigation for IV bags that were shipped to the customer without a thermal print label. Every time the operator pushed the emergency stop button, the printer and camera would lose their memory. The printer did not know what to print, and the camera did not know what to reject. We eliminated the problem by revising the PLC program to automatically reject the in-process bags following an emergency stop. We also added a verification clause to the validation procedure.
Use your imagination to think of other ways to adopt poka-yoke to pharmaceutical production.
Four Ways To Replace the Current Process With One That Is More Reliable
Change the current process by replacing it with a more reliable one. For example:
- Design a more robust screen for milling machines, so they don’t break so often.
- Add redundant sensors on machines so even if one sensor fails, the process is still OK.
- Replace human inspection with 100-percent automated inspection at the source. Install bar-code scanners.
- Install mechanical limiting devices or PLC programs so that a process cannot exceed a specified range.
Reduce Mistakes By Making the Process Easier
Make the process easier to perform so mistakes are less likely to occur. For example:
- Use “visual factory” techniques such as 5S and color-coding. Make errors more obvious.
- Redesign forms to be easy to complete and omissions easy to spot.
- Use dedicated storage areas to reduce the possibility of material mix-ups.
- Reduce material handling. Every movement is an opportunity to make a mistake.
- Add pictures to procedures.
How Can You Improve Detection?
Improve detection by adding new or better sensors at the source, if possible. For example:
- Add audible alarms or lights if a process is out of tolerance. Better yet, automatically shut down or add an interlock so the process cannot move to the next step.
- Use trending routines to signal before the process goes out of tolerance.
Understand that a corrective action that improves detection is inherently weaker than a corrective action that eliminates the problem. Why? Because detection does not prevent defects, it just prevents escapes. And defects cost you money!
Minimize the effect of the error. This is typically the weakest form of corrective action.
For most companies, product designs are constrained. Probably the only way to mitigate is to sort or rework, but this should be viewed as an interim step, not a permanent corrective action. This is true even if you design a perfect automated re-inspection system. Rework is a crutch.
Sometimes you can combine detection and mitigation. Here are some examples of what you can do:
- Install a metal detector with a link to the conveyor. When metal is detected, mitigate by stopping the conveyor before contaminating the bin.
- Use a camera to inspect fill volume and link it to a reject mechanism.
The Next Steps
Now that you are aware of the CAPA hierarchy, it is time to consider reviewing a sample of past CAPA actions. How many fall into the detection and mitigation categories (which are the least effective actions you can take)? The percentages will surprise you.
The CAPA hierarchy does not include retraining. Sometimes it isn't easy to identify the root cause. Just be careful not to fall into the “blame and train” trap when you can’t think of any alternative actions.
Training is necessary but not sufficient. What happens in six months when there is employee turnover? People are human, and people make mistakes. If training is one of the CAPA actions, be sure to supplement it with at least one additional CAPA that falls into the CAPA hierarchy categories listed in this article.
Roll out the CAPA hierarchy to your organization to implement better preventive actions that deliver significant improvements. With the CAPA hierarchy, you can anticipate an effective outcome rather than wait several months for the CAPA implementation only to be disappointed by the effectiveness check results.
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