What is “stop temperature?”

Return to Refrigerator Challenge” generates new questions from blood banks

This was the most common question we received from blood bankers in an unprecedented response to our January 2017 VUEPOINT.  In that issue of VUEPOINT, we shared the results of a “Return to Refrigerator Challenge” – where a major university hospital conducted a test to compare two blood temperature indicators.  Their intention was to evaluate indicator performance when unused blood was returned to the blood bank.

Although this was the first time we discussed stop temperature in a VUEPOINT, it’s not the first time we’ve received questions about it from our blood bank contacts. To address those issues, we researched what stop temperature means for indicator manufacturers who use this specification. We found that stop temperature appears to relate to the chemical indication behavior.  This means that if the blood product temperature is below the stop temperature, the indicator does not change color.

How does a 10oC indicator with an 8oC stop temperature behave?

The 10oC indicator used in the challenge has a specified stop temperature of 8oC.  If the blood product begins to exceed the stop temperature (8oC), the 10oC indicator’s chemical indication material melts back to its liquid state. This melting reaction gives users a visual indication that the blood product is no longer in compliance. This type of indicator may signal that the blood product is out of compliance once it exceeds 8oC, even if it never reaches 10oC, as shown in this example.

What does this mean to blood banks using a stop temperature type indicator?

Now that we understand what stop temperature is, the question is what does the specification – and indicator performance – mean to blood banks?  Specifically, what happens if the blood product is hovering around the 8oC stop temperature for any period?

Tests shared by blood banks, combined with our studies, have shown that under a wide range of exposures and times – once the indicator exceeds its stop temperature of 8oC, the indicator may be irreversibly tripped.  In multiple tests, the blood product temperature was being internally monitored to confirm that it remained below the indication temperature of 10oC before being returned to the blood bank refrigerator.  After the blood bags were returned to the refrigerator for reissue, many indicators had tripped during the refrigeration period.

Comments and questions from blood banks based on findings

  • “Doesn’t this make it an 8oC indicator?”
  • “We have many bags that are returned to the blood bank at 8oC and they look OK. We put them in the refrigerator and they show overheated.  This is an 8oC indicator.  We are throwing out good blood.”
  • “This did not show up in the standard validation, and it never occurred to us to try this while performing the validation. After performing the ‘return to refrigerator challenge’ we found that the indicator just did not perform”.

We are grateful for comments and questions like these because they help fuel our blood indicator knowledge and testing.  Clearly, the “stop temperature” specification may be new to many blood banks and is something to be further explored.  Please share your experiences and observations so we can continue learning together.

HELP not HYPE: Being truly useful to blood banks

VUEPOINT posts and website top-ranking pages prove that delivering blood bank help is timeless and valuable

The Williams Labs web site was created with a single goal – provide a place where people involved in blood banking can find information to help them perform their jobs more easily and with better results.

We are delighted that blood bankers from around the world – some who are Safe-T-Vue users and some who are not – routinely visit williamlabs.com and read our VUEPOINT posts because we are providing relevant, useful and helpful information for blood banks.

AABB_Temperature_Standards_2016We’ve also been flattered to learn that blood bank inspectors point blood banks to our website as an easy source of information regarding transport and storage of blood products.

In this VUEPOINT, we share the links to these pages and posts as a quick guide to these informational resources. Maybe they are handy to bookmark for your daily blood bank operations – or perhaps in orienting a new employee? Whatever your reason, it’s here for you and your blood bank staff – with our continued focus on helping you do your best.

Top 5 Useful and Helpful Pages

1. AABB Temperature Standards for Blood Products: Storage and Transport
This table provides fast access to the newest 2016 AABB Reference Standard 5.1.8.A for storage and transport temperatures of blood components.

2. Simulated Blood Product RecipesSimulated_Blood_Products_Validation
We first published this VUEPOINT almost 4 years ago, and based on the web statistics, it continues to be a valuable resource for blood banks. Did you know that 10% glycerol in water is NOT “one size fits all?” You might want to read this one and learn more.


3. QA Documents
It doesn’t sound glamorous or intriguing, but the incredibly useful nature of having QA documents for the Safe-T-Vue products easily accessible 24/7/365 has proven to be a winner. No hype, just help.Safe-T-Vue_QA_Docs

4. Category: Storage of Blood Components
This page provides titles and excerpts of all the VUEPOINT posts in the category “Storage of Blood Components” that we’ve published over the years. Scroll down the page and you’ll quickly find information on IR Thermometers, Cooler Validation, Refrigerator Setpoints, Indicator Comparisons and more.

5. Tags: Blood Temperature
Similar to #4 “Storage of Blood Components” this page presents almost 5 years of VUEPOINT posts that have something to do with blood temperature – measuring, monitoring, and managing.

We are always looking to learn from you – about how we can be more helpful and genuinely useful by providing valuable information to blood bankers worldwide. If you have suggestions for VUEPOINT topics or questions you’d like for us to explore – and share – we would be delighted to hear from you.


Jeff Gutkind

Cooler Validation: Comparison of “Manual” Thermometer vs. “Automated” Data Logger Methods

In our March 2012 survey of over 70 blood banks, many respondents generally described cooler validation as a “pain,” characterizing it as time-consuming, frustrating and even primitive.

Most blood banks revalidate their transport coolers annually. And although it is only once a year, there never seems to be a good time or resource-efficient way to do it.

Using multiple data loggers allows more accurate temperature mapping of the cooler interior.

The three key factors we hear repeated most often are:
1. Time Efficiency (technician’s time)
2. Data Accuracy
3. Simplifying Documentation

At the SCABB/CBBS meeting last month, we entertained compelling discussions with blood bankers who have switched from manual cooler validations with thermometers, to using data loggers (electronic temperature recorders). Some of them are using the Val-A-SureTM Cooler Validation Kit.

If you’ve ever considered switching to an automated validation process, we thought it might be helpful to share what we’ve learned from blood bankers across the country. In the following table (next page) we compare the traditional “manual” thermometer method to the “automated” data logger method – and capture how it has changed their validation experiences.

This graph displays temperature of the top bag vs. the bottom bag. The data is downloaded from data loggers and printed for permanent validation documentation, eliminating handwritten and transcribed data.

We’ll be giving away a Val-A-Sure Cooler Validation Kit at AABB 2015, so if you’re interested in a “free” chance to change your cooler validation method, be sure to stop by and see us!

Jeffrey Gutkind

P.S. For more on Transport and Storage Coolers, check out our Tips, Helpful Ideas and AABB Standards References on www.williamlabs.com.

COMZ VUEPOINT – Cooler Validation-Comparison of Manual Thermometer vs. Automated Data Logger Methods – web version (doc. 2341)

Blood Bank Refrigerator Setpoints Matter

Learn about these important time/temperature correlations relative to your day-to-day blood bank operations.

Understanding the time pressures of busy blood banks, it would be fair to say that ANY time/temperature “advantages” – such as revisiting the refrigerator setpoint – might be worth consideration. Learn more in this VUEPOINT.

by Jeffrey Gutkind, Temptime

Over the past several months I’ve had the opportunity to visit some of the largest blood banks across the nation. In the course of talking with blood bankers about maintaining blood temperatures during storage, issue and transport, I observed a wide range of refrigeration setpoints, anywhere from 1.5oC to 4.7oC.

Reviewing my observations from these visits and reflecting on the AABB standard of 1.0oC to 6.0oC for storage, it brought me back to the “starting” temperature for blood when it’s removed from the refrigerator.

    • How does even a degree or two at a higher or lower storage temperature affect the blood temperature as it is dispensed and issued from the blood bank?
    • More importantly, how does the refrigerator setpoint affect how much TIME you have before the blood reaches 6oC?

To answer these questions, we asked Marielle Smith, Technical Service Scientist, to run a simple test in our lab.

How long does it take for refrigerated blood products to reach 6oC?

Blood Storage Temperature: 2°C vs. 4°C

The following table and graph show the time it takes for the core temperature of a refrigerated blood bag to warm to 6°C when removed from refrigerated conditions (2°C or 4°C) and placed on a counter-top at room temperature.1

The graph demonstrates that the lower the refrigerated storage temperature, the more time it takes for the blood bag to reach 6°C when warming at room temperature conditions. While these results are specific to the test method and setup used, they should be typical.

In terms of practical, day-to-day blood bank operations, what does this tell us?

Based on this test data, it suggests that blood bankers have over twice as much time to get blood issued and dispensed when the refrigerator setpoint is lower (2oC vs. 4oC). This represents a significant advantage for refrigerating blood at lower temperatures and longer times out of refrigeration before the blood goes out of specification.

Knowing that AABB guidelines state blood can be stored at 6oC for up to 42 days and transported between facilities below 10oC, and at the same time understanding the time pressures of busy blood banks, it would be fair to say that ANY time/temperature “advantages” such as revisiting the refrigerator setpoint might be worth consideration.

What do the blood refrigeration experts have to say?

After researching refrigerator setpoint specifications for a number of different vendors, we found that the factory setpoint is typically 4.0oC. Not being a refrigerator expert, I decided to reach out to Colleen Holtkamp Market Manager from Helmer® Scientific, to learn more. Colleen graciously provided these thorough answers to my questions, as well as thoughtful guidance for your consideration on setpoints, alarms and refrigerator specifications. (Colleen’s responses are in blue following the questions).

1. What is the typical factory setpoint temperature of your refrigerators when they go into the field? Are these setpoints easily changed, or does it have to be reset by the factory?

“The typical setpoint for Blood Bank Refrigerators is 4oC. Per AABB Standards, the acceptable temperature for storage of whole blood and most red cell components is 1oC to 6oC. Setting the temperature to 4ºC, close to the middle of the range, is standard practice for blood bank refrigeration.

It should be noted that the alarm setpoints are important, as well. AABB Standards state that alarms should be set to activate before blood components are exposed to unacceptable conditions. For example, since the lower limit for blood storage is 1oC, it makes sense to set the low alarm to 1.5oC (and since the upper limit is 6oC, a high alarm setting of 5.5oC is appropriate).

The ability to change the temperature setpoint depends on the manufacturer/brand of the refrigerator, as does the process for changing the alarm settings (instructions should be included in the refrigerator’s user manual).

Helmer Scientific Blood Bank Refrigerators enable the operating setpoint and alarm settings to be changed at the facility (they do not have to be reset by the factory). With temperature and alarm settings, it’s important to remember that while it should be reasonably convenient to modify them, it shouldn’t be so easy that they tend to be changed by mistake. A safeguard such as password protection for the refrigerator settings offers the best of both worlds – security and ease of use.”

2. Is there some type of statistic that you would use to say if the door is open for 3 minutes per hour; it will take XX minutes to get back down to the original setpoint?
As an example: If the refrigerator is set to 3.0oC and the door is open for 2 minutes, how long will it take for the refrigerator to get back down to the 3.0oC setpoint?

“There isn’t a standard method for measuring temperature recovery after a door opening. It can be impacted by variables such as ambient temperature and how much cold product is stored in the refrigerator at the time. What is important is that the unit has a heavy-duty, forced air refrigeration system and that the fan stops running while the door is open so that it does not blow out the cold air. In addition, the refrigeration system should be powerful enough to circulate the air inside the cabinet multiple times shortly after the door is closed, ensuring quick temperature recovery.

Another consideration is the importance of alarms. Having both a door open alarm and a high temperature alarm provides two layers of protection against temperature excursions due to door openings.”

3. What is the typical tolerance for blood bank refrigerators? (we found this information difficult to find in our online research).

“Blood Bank requires the tightest temperature uniformity of any cold storage application. The typical temperature uniformity specification for Blood Bank Refrigerators is +/-1oC. While not necessarily a regulatory requirement, many Blood Banks have written this specification into their internal protocols/SOPs. Therefore, it has become a community standard that drives performance expectations for Blood Bank Refrigerators.

Before a Blood Bank considers changing refrigerator setpoints from 4oC to 2oC, it is critical to think about the following information. If a blood refrigerator is set to 2oC, with uniformity of +/-1oC, the temperature inside the unit might reach the lower limit of the acceptable range (1oC). Also, if the low alarm is set to 1.5oC (which is advisable because AABB standards state that alarms should activate before blood is exposed to unacceptable conditions), it may be triggered by operation at 2oC. Helmer Scientific’s priority is to optimize the temperature of the blood bag while it is stored in our units. The setpoints and alarms are established to protect the blood while it is in the refrigerator.”

When it comes to blood bank refrigeration setpoints, what have we learned?

• The typical factory setpoint for blood bank refrigerators when delivered from the manufacturer is 4.0oC
• The ability to change the refrigerator setpoint at the blood bank varies by manufacturer
• Blood that is stored at 2oC takes over twice as long (approximate, based on our test) to reach 6oC at ambient, when compared to blood stored at 4oC
• Temperature recovery of refrigerators is affected by a number of variables (door opening, amount of stored cold product, ambient operating temperature)
• Low and high alarms, as well as open door alarms, are important and recommended by the manufacturers

If you have any recommendations, experiences, questions or ideas relative to refrigerator storage temperatures and your blood bank, we’d love to hear from you. Please POST A COMMENT or email us.

Jeffrey Gutkind

1Test Details
At each storage temperature, a total of six (6) simulated blood bags were tested. Each 600mL PVC blood bag (Charter Medical) was filled with 350mL of a mixture of 10% glycerol and 90% water, to simulate red blood cell volume. The bags were removed from refrigerated storage (at 2°C and 4°C) and then placed lying flat on a counter-top at room temperature (at approximately 21°C with 30% R.H). The temperature was measured by placing a calibrated temperature-sensing probe in the center of the simulated blood mixture inside the bag and the temperature was monitored using a calibrated Oakton Thermistor Thermometer. Temperature readings were recorded at 1 minute intervals. The data represents the time needed for the simulated blood mixture (10% glycerol with 90% water) to warm to 6°C.

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Are all temperature indicators created equal?

When it comes to cost and performance, how do you choose?

by Jeffrey Gutkind

In today’s cost-conscious healthcare environment, our immediate reaction when making a buying decision is to minimize purchase cost.   The temperature indicators currently on the market have different costs.  And there are questions you may be asking:

  • is the “cheapest” purchase price going to save the blood bank money overall?
  • are all indicators equal in terms of performance?
  • how do you know which indicator to choose?

To answer these questions, let’s take a step back and question WHY we even use temperature indicators.

Temperature indicators for blood products were originally designed to provide assurance that blood product temperatures had not exceeded AABB temperature guidelines when the blood is out of the blood bank’s control. The temperature indicator provides proof that the blood product has been maintained at proper temperature while out of the blood bank control.

Numerous visitors to our AABB booth a few weeks ago stated that 40-50% of the blood issued from their blood banks is not used. To further illustrate the challenge, a journal article recently published in Transfusion (shared in our August 2014 VUEPOINT), described a study by a blood bank that stated how most of their blood waste was from either temperature or time (away from the blood bank) excursions, and that 70% of those losses came from blood products issued to the OR in coolers.  Temperature indicators are used by blood banks worldwide for exactly this reason – to provide assurance that the blood products at no time exceeded temperature thresholds, to help maintain blood product quality and to minimize blood waste.

So, other than cost, what matters when choosing an indicator?

Let’s circle back to our initial questions of the temperature indicator cost and the temperature indicator performance.  Since the job of a temperature indicator is to provide temperature information back to the blood bank, the indicator’s temperature ACCURACY (also referred to as “tolerance”) is critical.

As an example, of the three most popular 10o C temperature indicators on the market today, each publishes a different accuracy specification:

  • Safe-T-Vue 10  +/- 0.4 o C
  • Indicator A +/- 0.5 o C
  • Indicator B +/- 1.0 o C

How does indicator accuracy influence blood product waste?

In this illustration, you can see that a 10oC indicator with an accuracy of  +/- 1.0 may actually “trip” at 9 o C, thus falsely indicating that the temperature of the blood is out of specification.  And, as we all know, the cost of wasted blood itself far exceeds the purchase price of an indicator – and minimizing blood waste (not indicator cost) is the primary objective behind using a temperature indicator.

Using an average cost of $250.00 for a single wasted blood unit, it’s easy to calculate the potential savings of using a more accurate temperature indicator.   The cost difference in temperature indicators is minimal in comparison to the cost of one wasted unit of blood.

When comparing temperature indicators to make a buying decision, be sure to make ACCURACY comparison a key factor in your selection process.  Safe-T-Vue indicators are available in 6°C and 10°C temperature indications, both accurate within +/-0.4°C.  *

As always, we welcome your comments and feedback on the ideas presented in this VUEPOINT.


Jeffrey Gutkind

* Refer to AABB standards for blood banks and transfusion services, 21 CFR 640.2, 21 CFR 640.4, and 21 CFR 600.15.

How can you monitor CORE blood bag temperature with adhesive temperature indicators?

With several indicators on the market, it’s increasingly confusing to know what to use – or who to trust.

There’s been a lot of “buzz” lately about measuring core temperature of blood units during temporary storage and transport.  Do the adhesive temperature indicators on the market, including Safe-T-Vue, measure core temperature?

The simple answer is NO.

Since all of the available temperature indicators are applied to the blood bag surface, they do not measure core temperature. As most of you know, there is no way to measure core temperature of a blood unit during temporary storage and transport without inserting a temperature probe into the “core” of the bag.

So, if the indicators aren’t sensing core temperature, what are they sensing?

These adhesive temperature indicators are actually measuring the surface temperature of the bag, not core temperature.  Safe-T-Vue also measures the surface temperature of the bag. However, through over 20,000 laboratory tests, we have developed direct correlations between blood bag surface temperature and core blood product temperatures.  This process allows us to formulate a consistently performing adhesive surface indicator, and assures that Safe-T-Vue indicator response is accurately correlated to actual core temperatures.

How can you trust the performance of a temperature indicator?

1. Published product specifications

Suppliers, like William Labs, publish the temperature accuracy of their products, usually in their product literature and on their websites.

Safe-T-Vue has correlated temperature indication to core blood bag temperature supported by over 20,000 test data results that quantitatively support the consistency, predictability and repeatability of its indicator performance.

2. QA Documentation

Some suppliers take the “proof” of temperature accuracy a step farther, by supplying their customers with QA documents and procedures, documenting the temperature data for that product, for each lot, to prove that testing was performed and the product performs to specification.  Safe-T-Vue is shipped with accompanying QA documents, which can also be accessed anytime from our website.

For added confidence and convenience, the validation procedures for Safe-T-Vue are published on the website, for those users who would like to perform their validations and replicate our work in their own labs.

3. FDA 510(k) and Quality Audits

As you know, the purpose of the FDA is to oversee safety.  Section 510(k) helps the FDA make sure new medical devices are safe and effective. New medical devices submitted under 510(k) rules must also be “substantially equivalent” to other similar marketed products.

This FDA regulation that applies to medical devices, including temperature indicators, is of critical importance.  It assures that the supplier of the product you are trusting to “do its job” is both safe and effective.  510(k) ensures the product is as safe and as effective as other 510(k) devices already on the market.

Just because a product is being sold into the healthcare market, do not assume it has been cleared by FDA 510(k).  Ask your supplier – and make them prove it.

Additionally, credible suppliers have a quality plan to support the process and accuracy claims of their products.  For example, actual and statistical verification of Safe-T-Vue data supports the product claims.  As part of the quality plan, this data is reviewed by the company’s QC staff and annually by external auditors.

What’s next?

We’ve been so stimulated by the recent conversation about core temperature, that we’re making plans now for comparative studies in early 2014, which we will be sharing with you.  Our new partnership with Temptime has expanded our time-temperature testing capabilities and laboratory expertise in healthcare, so look forward to these and other test results in the coming year.

As always, if you have any thoughts on core temperature measurement and adhesive temperature indicators, we always appreciate hearing from you.  Feel free to post a comment on the VUEPOINT post, or email us.

Blood Temperature Compliance at 6°C … is it safe to re-inventory?

When blood products are issued from the blood bank in a packed cooler and are later returned to the blood bank, how do you know if the blood was maintained at the compliance temperature of 6°C? In this 90 second video, you’ll see how Safe-T-Vue® 6 from William Laboratories (www.williamlabs.com) can be used throughout the transport and temporary storage process to provide easy visual indication if the blood temperature exceeds 6°C.

Val-A-Sure Cooler Validation Kit Overview & Introduction

The Val-A-Sure™ Cooler Validation Kit from William Labs (williamlabs.com) combines everything you need in one simple kit for temperature validation of blood transport coolers. All of the necessary components, instructions and documentation for validation are conveniently included in the kit, and have been tested to work together efficiently and accurately.Hands-on trials and feedback from blood banks and laboratories provided the guidance for the Val-A-Sure™ kit development. It delivers the simplicity, accuracy, standardization and speed of process that blood banks and labs told us that they need — in one integrated kit.

Recommended SOPs, temperature recorders and software provide options for an accurate validation process, regardless of your blood bank size. Using electronic recording equipment and following the SOPs, and using the supporting documentation, helps ensure consistent measurement and recording for each validation.

The DVD and documentation supplied with the kit contain:

– QuickStart Guide
– Easy-to-follow 3 minute video instructions of 3 different recommended validation procedures
– Validation SOPs (4 included)
– Validation Log Sheet
– Cooler Label format/template
– Validation Tips