Controlling medical device monitoring and measuring equipment is an essential element of an ISO 13485 QMS. Monitoring and measuring equipment verifies that a medical device is safe to put on the market, so any issues with the equipment’s accuracy can put patients at risk.
This article will provide a guide for understanding and implementing the Control of Monitoring and Measurement Equipment by breaking down ISO 13485 section 7.6 in a way that’s practical and simple to understand.
Table of Contents
What equipment needs to be controlled?
First, let’s break down some terminology. According to the ISO 13485:2016 Practical Guide:
- Monitoring is supervising, checking or observing over a period of time, and
- Measurement is determining a quantity, magnitude, or dimension, by using measuring equipment.
A big piece of controlling monitoring and measurement equipment is calibration. However, ISO 13485 does not provide specifics about what equipment needs to be calibrated, how it is calibrated, or the frequency of calibration. That means it is up to the organization to determine its own needs for calibration.
That being said, organizations cannot choose to forgo calibration completely. Measurement equipment that is used to verify the accuracy of a medical device or its components should be calibrated. The language in ISO 13485 is that “equipment needed to provide evidence of conformity of product to determined requirements” requires calibration.
Determining what equipment needs to be calibrated varies for organizations depending on the nature of their products. There are mechanical devices that rely on handheld tools for measurement such as micrometers and calipers, as well as devices that rely on heavily automated digital equipment. Software, cameras, pH meters, thermometers, time-keeping devices, and more could all require calibration depending on the situation.
An easy way of thinking about what measurement equipment should be calibrated is to work backward from an audit. During an audit, it is likely that process records, as well as incoming, in-process, and final inspection records, are reviewed. The records should include what equipment is being used during the process or inspection.
Therefore, if monitoring and measuring equipment is used during any type of inspection or for monitoring any processes, the equipment should be calibrated. Measuring equipment should also be calibrated if it will be used during design verification or validation testing.
What measurement equipment does not require calibration? Reference equipment is typically not included in the calibration requirements of ISO 13485. If measuring equipment is only used during R&D (and won’t be used for design verification or validation), or if it is used to aid in the construction of molds that will eventually produce medical devices, it may not fit into the requirements of the standard.
That said, measuring equipment that is not calibrated will never provide a confident result. Companies should strive to only use calibrated equipment to maintain accuracy through all processes.
Other types of equipment that do not need calibration include:
- General office instruments, such as clocks and thermometers in place for employee comfort that are no involved with process control.
- Equipment only used for indication, such as a process gage used to ensure the existence of line pressure
Ultimately, it is still up to the organization to determine the risks of not calibrating certain pieces of measuring equipment.
Requirements for a calibration procedure
ISO 13485 section 7.6 states that an organization must have a defined procedure for performing calibration of control of monitoring and measurement equipment. Let’s look through the specific requirements of this section to highlight what needs to be included in the procedure.
Calibration intervals and standards
Measuring equipment must be calibrated both before use and at specific intervals. If a piece of measuring equipment has been recently purchased the organization can sometimes rely on a calibration certificate provided by the manufacturer to satisfy these requirements. Other times, measuring equipment is installed on-site by the manufacturer or distributor and is calibrated at that time (this is common for CMMs and optical tools).
The intervals for calibration will also be determined by the organization, but they cannot get too liberal with the length of calibration intervals. Not only will calibrating a piece of equipment every five years not prove reliable, but it also means that a significantly larger amount of product is at risk. In general, companies should rely on the calibration interval specified by the equipment manufacturer if possible.
Calibration must be traceable to international or national measurement standards. There should be a line from all pieces of measuring equipment to the standard that it is calibrated against.
Sometimes there is no standard for a piece of measuring equipment, such as a gauge that is produced in-house. In this case, the organization must create its own standards and specifications for which the equipment will be calibrated. The company should justify its use of company-specific standards and they should validated and traced to product specifications.
Adjusting calibration equipment
The next requirement is related to adjusting or re-adjusting measuring equipment. Measuring equipment must sometimes be adjusted to perform properly or meet calibration standards.
If equipment does need to be adjusted, the adjustments should be recorded. That way, the organization can demonstrate that the adjustments were done to specified procedures, and show the effect of the adjustments on the equipment. Sometimes the device requiring adjustments will have been found out-of-calibration, which we will discuss later in this article.
Identifying calibration status
All of the measuring equipment a company uses must be easily identifiable. This means that there is a specific gauge or equipment number listed on the device. If a company has multiple micrometers, for instance, all of the micrometers must be able to be traced back to their specific calibration records.
A company has the option to rely solely on the original equipment manufacturer’s serial number, but these are often lengthier than needed. Most organizations choose to create their own gage-numbers and tie those into the manufacturer’s serial number in their records.
The calibration status also needs to be identifiable for all pieces of measuring equipment. This is often done through the use of calibration stickers which list when calibration was performed, when the next calibration is due, and the name of the person who performed the calibration. This is beneficial because production workers can quickly tell if a piece of equipment is out-of-calibration, and refrain from using the equipment (it is essential that measuring equipment that is out-of-calibration is not used for monitoring or measurement.
However, calibration stickers will not fully satisfy this requirement. The organization should also be able to determine the calibration status of all of its equipment without having the equipment present. This is typically achieved through the use of spreadsheets or calibration software. Some eQMS software includes a module for calibration, which the organization can easily access to pull the calibration status for its equipment.
During an ISO 13485 audit, an auditor will either look at the calibration stickers on different pieces of equipment to understand the calibration status, ask for the calibration status for all pieces of equipment, or both. For this reason, it is crucial that organizations are fully aware of their equipment’s calibration status. An auditor identifying a piece of equipment that is out of calibration while walking the floor is one of the easiest audit findings for an organization to receive.
The person performing the calibration should also be documented and included with the calibration record. This can be an employee of the organization or a contractor who is brought in to perform calibrations.
Safeguarding and protecting equipment
The next requirements are that calibration must be safeguarded from adjustments, and protected from damage during transportation and use.
Safeguarding a piece of equipment will vary based on the specific piece of equipment that is being used. Let’s look at the example of a coordinate-measuring machine (CMM). A CMM typically has a large number of adjustments that can be made via software so that it is properly calibrated and functions correctly. Typically, access to the adjustments is password protected so that operators cannot adjust the equipment either accidentally or intentionally. The password is what safeguards the equipment from adjustments.
Protecting the piece of equipment will also be dependent on what the equipment is and how it is used. Some gauges should be kept in boxes so that they are less prone to damage if dropped or exposed to the changes on the shop floor. Very technical pieces of equipment may need to be kept in a lab so that they are not impacted by dust or grease from the production floor.
An organization needs to consider how and where measurement equipment is being used when it puts protections in place. It should also train operators to bring pieces of equipment that have been dropped or damaged to the quality or metrology department immediately. That way, the metrology department can quickly adjust and recalibrate the equipment before it is used on production units.
Documenting calibration procedures
ISO 13845 states that organizations must have specific procedures in place for calibration and verification.
If organizations will be performing calibration themselves, they must have work instructions documented for the specific steps necessary to complete calibration. The work instructions should include what the tolerance requirements are for the calibration to be considered successful, the equipment that is used for the calibration, and any traceable standards related to the calibration. Employees who will be performing the calibration should have the work instructions readily available and be trained on the procedures.
If the organization is going to send out monitoring and measurement equipment for calibration by an outside company, they still maintain responsibility for the process. The calibration supplier should be qualified according to the organization’s supplier management process, and the organization should review the calibration records to ensure they include all needed information.
The calibration procedure should also include how calibration records will be stored, as this is a requirement of ISO 13485 and the FDA. The calibration records can follow the organization’s general document control procedures or be kept in the calibration software if that is available.
What happens when equipment fails calibration?
One significant piece of the control of monitoring and measuring equipment for medical devices is what must be done if measuring equipment is found to be out of calibration at any point.
If a piece of measuring equipment is being calibrated it must first be checked to see if it meets its specified requirements. The result needs to be recorded and included in the calibration record. If an organization is working with outside contractors it must ensure that the “as-received” condition is recorded on the calibration certs.
If a piece of measuring equipment fails calibration or does not meet its requirements the organization must perform a risk analysis for the equipment. The risk analysis can include several steps depending on the product and organization:
- Determine what products were inspected with the measuring equipment. All inspections should record what measuring equipment was used during the inspection. That way, there is a traceable line from the measuring equipment to the inspections.
- Review the results of the inspections to see if there were any inappropriate non-conformances demonstrated or unusual inspection results. The inspections may also have been completed with different pieces of equipment (such as multiple inspectors using different calipers). In this situation, if the inspection results are consistent within a lot, the organization can support that there was little risk as a result of the out-of-tolerance equipment.
- Reinspect any affected product that is still on-site at the organization. This can help understand the actual impact on the product which was inspected with the out-of-tolerance equipment.
- Compare the out-of-calibration results to the device specifications. If a micrometer was found to be out-of-calibration by .001″, but all of the affected products have dimensions with much larger tolerances, the effect may be minimized.
- Investigate if there were any complaints generated as a result of out-of-tolerance equipment.
- Consider the risk level of the process where the measuring equipment was used. If the equipment was used at the very beginning of the manufacturing process, there may be less impact on the finished device. However, if the equipment was used as part of the final release of the product the impact may be quite significant.
Based on the results of the investigation the organization will have to initiate remedial actions. The organization might determine that there was no risk to finished devices as a result of the out-of-tolerance measuring equipment. On the extreme end, the organization might have to initiate a product recall or safety notice if there is a significant and dangerous impact from the equipment.
Ultimately, it is up to the organization to determine the risk and impact related to equipment found out-of-calibration and the necessary actions that must be taken. The analysis and actions should be appropriate to the risk level and must be recorded and readily available.
Software Calibration
Finally, ISO 13485 requires companies to validate any computer software that is used to inspect the requirements of devices. There are many different pieces of monitoring and measuring equipment that have a software component, such as a CMM. If the CMM will be used to verify product requirements, then the CMM will require validation.
In this scenario, the CMM might be validated by itself, and any programs that will be used to inspect product requirements will be validated individually. This should be done prior to using the CMM during production, as well as any time the CMM changes or is moved.
The organization will also have to follow the previously mentioned steps if the CMM is found to be out of calibration at any point. The calibration information and validation should be recorded.
Summary of a Calibration Procedure
Using everything we’ve discussed so far, I’m going to provide a list of items that should be in a company’s control of monitoring and measuring equipment procedure to remain compliant with ISO 13485:
- How pieces of monitoring and measuring equipment will be identified, how their calibration status is identified, and where this information is stored.
- The frequency and manner in which monitoring and measuring equipment will be calibrated.
- The process used to calibrate monitoring and measuring equipment.
- How software used for monitoring and measuring is validated and revalidated.
- A process that includes determining if equipment does not conform to its specifications, actions that will be taken in that situation, and how the actions will be recorded.
- How monitoring and measuring equipment will be safeguarded from adjustments, and protected from damage and deterioration.
- The way calibration records will be stored and maintained.
Wrapping Up
That was an overview of what is required for the control of monitoring and measuring equipment used for medical devices based on ISO 13485 section 7.6. Inspection and calibration play a significant role in the safety of medical devices, so organizations must have well-established calibration procedures.
If you have any questions or comments about the calibration of equipment used in the production of medical devices, please leave a comment below. Also, if you found this article helpful, check out our ISO 13485 page for other ISO 13485 guides and sign up for our newsletter below.