Video Q&A: Data logger accuracy & resource savvy re-qualifications

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In this video interview, Vaisala Senior Regulatory Expert answers three questions from customers and industry contacts. If you have follow-up questions, please feel free to comment on this page or email us.

[00:00:08] Greetings again from Vaisala. My name is Janice Bennett-Livingston, I'm the life science marketing manager here at Vaisala and I’m joined by Paul Daniel, Senior GxP Regulatory Expert. We are going to do another Q&A session this morning and Paul will answer some questions we've received by e-mail from some of our contact and some of our customers. So let's jump right into questions. OK, Paul?

Paul: Sounds good.

[00:00:59] All right. So question one: “What are the acceptance criteria in a mapping study for temperature compliance between monitoring and mapping loggers? My mapping sensors have an accuracy of ± 0.5 degrees Celsius, my monitoring loggers are ± 0.3°Celsius. Many of them are placed beside each other and some of them are showing values that are different by more than 0.8°C. I can't find anything that tells me if this is a problem or not.”

[00:01:32] Paul: Ok. Well, the simple answer is that you are monitoring and mapping sensors - they do not need to have perfectly matching values. Sure, it's nice when they do, but the requirement of mapping is to verify the accuracy of the sensors, not by comparing them one against the other, but by verifying that they've been calibrated.  For the monitoring loggers, there should be a valid annual calibration certificate.  And for the mapping sensors, there should be a pre-cal and a post-cal to show that they were calibrated before and after the study.  That’s your acceptance criteria, the one that matters, when it comes to the verification of sensor accuracy.

It's really easy to think that two calibrated sensors should have almost the same reading, but that’s only going to happen in a tightly controlled environment like a calibration lab. What you are probably seeing in your mapping is an uncontrolled comparison that has a large element of measurement uncertainty. There's probably some air-flow through the area that's changing things up, as well as like a difference in response times and resolution between your two sensors. This will make a true comparison really difficult. Measurement uncertainty can only be quantified under controlled situations by a qualified metrologist, which is what happens in a calibration lab. If you're mapping loggers have that accuracy of 0.5°C and your monitoring probe has the accuracy of 0.3°C, then it’s not impossible or that unlikely to see a 0.8°C difference and it certainly doesn't mean anything is wrong. If your mapping protocol doesn't include specific criteria that the sensors should match perfectly, or match within a certain amount, then all you can do really is verify that the sensors are properly calibrated.

[00:03:22] Ok, question two.

“I have to periodically re-map our temperature controlled rooms. I'm trying to determine whether during temperature requalification it should be done for 24 hours or 72 hours. The initial studies were 72 hours and I'm wondering if this needs to be done under static or dynamic conditions. My gut is to lean toward a 24-hour static full chamber study. The reasoning is that we've already proven 72 hours of empty chamber and loaded chamber static/dynamic conditions. This is just a verification that everything is still in a qualified state.

“I do not want to overkill a study, but I've searched high and low on the Internet and there is a ton about initial qualification in all aspects of qualification/validation. But there's not much for performing re-qualifications/re-validations. I've looked at the World Health Organization, the FDA, EU etc. I've come up empty and hoping you can help.”

[00:04:34] This customer’s experience matches my own experience and findings. There's a lot of information on mapping and initial qualification, but there's almost nothing, no information on requalification. The best resource I've found for this is from the ISPE, (the International Society of Pharmaceutical Engineers) in their good practice guide for Mapping Controlled Temperature Chambers. Sometimes I feel a little embarrassed recommending this guide because I contributed to it. But obviously you don't care because you're listening to me talk right now. The ISPE guides can be kind of expensive— around $300 or so. But, if you're doing any serious work in temperature mapping, it really worth getting yourself a copy. The ISPE guide I just referred to basically tells us to re-map every one to five years. That's based on performance, history and criticality of the given space that you're mapping. They recommend that you document your approach and use a risk assessment to justify your choice and double-check those decisions.

This is exactly what this customer suggested they would do — a shorter mapping of a full chamber while it's still in use. This approach is perfectly consistent with the ISPE’s recommendations in the guide. This makes sense to me if there has been no history of malfunctions or repairs on the unit. Also it's just easier to map something loaded because you don't have to convince the owner to empty their chamber just for your study.

[00:06:03] Ok question three…

“I am wondering if Vaisala has any papers that address warehouse changes in the midst of fast-changing business needs? I'm responsible for mapping warehouses at our company. They keep making changes to the warehouses, which means I have to keep remapping them. I don't foresee the changes stopping soon. Is there any model to just map the changed area, or to not do seasonal mappings after a change?”

Paul:  I really appreciate that this customer is trying to maintain compliance in what is a pretty difficult situation. My experience is that most folks don't take their warehouse mapping seriously enough and do regular re-mappings, including seasonal mappings. There are a few things we can do to lower our mapping requirements, but it's just the typical risk based arguments about why mapping part of the warehouse is OK or why a non-extreme seasonal mapping is OK as well.

But all these arguments can only be used if you already have a good mapping history to draw upon. You really need to understand the basic temperature dynamics of the warehouse space to make conclusions about how it will behave in other situations. This is how you get to the place where you can confidently say: I don't have to map the whole thing. If you don't have that background and that basic understanding, then you can't make a statement like that.

I think this situation is a perfect case for a practice I call “continuous mapping.” This is basically the same as temperature monitoring, but you use the same number of data loggers as you would use for mapping. So you're going to be monitoring with two, maybe three times more loggers than usual.

I know this sounds expensive at first because you have to buy more loggers and you have to keep them calibrated. But when you do the math, honestly, you save money on every mapping because the mapping is so much easier. You don't have to maintain mapping loggers, or rent mapping loggers. There's no wasted time deploying loggers with a scissors lift or a forklift up to the dangerous top of the warehouse stacks way up there, 10 meters up. All those time savings makes it cost less. Especially when you're dealing with a situation like a customer who's having to map the warehouse yearly just to keep up with the pace of changes.

With this continuous mapping model, you still need to do the validation part. You still need to go in and select a time period and officially verify performance by looking at the data. But it becomes a lot easier when all we have to do is grab data from a given time period.

I'll take a moment to give a plug for our upcoming webinar on exactly this topic: continuous mapping for warehouses. It's later this month and if you're interested come on down and join us.

[00:09:08] Yes, please join us June 24th for our webinar: Continuous mapping: better data, better, compliance. If you happen to see this video after the 24th, the webinar in its entirety will be available for you to watch on demand. Thanks for joining me, Paul, and thanks to everyone who watched. Stay well everybody!