Among the world's largest clinical laboratory networks, Labcorp operates over 2,200 patient service centers and supports more than 6,800 in-office phlebotomists across the United States. Labcorp transports thousands of temperature-sensitive samples each day, operating under strict turnaround targets of one to two days for most diagnostic tests[0].

Labcorp evaluated each shipping solution’s ability to maintain internal temperatures within the critical refrigerated (2–8°C) range for temperature-sensitive shipments. The Medstow Micro shipper sustained refrigeration temperatures twice as long as a passive alternative under simulated summer conditions. Meanwhile, during simulated winter conditions, the Medstow Micro sustained target temperatures when the passive shipper failed to maintain refrigeration altogether.

Environmental Setup

This testing followed Summer and Winter Shipping Challenge Profiles used to simulate temperature conditions that a product might experience during ambient shipping and distribution. Such profiles are often used for stability studies and package validation to meet FDA expectations for shipping qualification.

For both the Summer and Winter Shipping Challenge Profiles, performance is evaluated based on the container’s ability to maintain a stable internal temperature range of 2–8°C refrigeration. Specifically, to meet performance criteria, the container must sustain this temperature range for a minimum of 8 continuous hours. Throughout the 72-hour testing window, containers are allowed up to one hour of deviation outside the 2–8°C temperature range. This strict standard ensures reliable thermal protection under both summer and winter conditions.

In this evaluation, Labcorp tested two packaging solutions:

• A small Styrofoam® box with two 8 oz gel packs (typical for small shipments)

• Artyc’s Medstow Micro

Both packaging solutions were placed in a temperature-controlled chamber. In advance of testing, each package was preconditioned according to the following guidelines:

• The 8 oz gel packs were frozen 24 hours in advance in an onsite -20ºC freezer

• The Medstow Micro was charged overnight

Results and Observations

Data was generated for 72 hours in total in the test chamber. The Styrofoam box shipper was monitored for internal temperature at 5 minute intervals. For this study, the Medstow Micro logged temperatures at 10 minute intervals. (The Medstow Micro is capable of logging at 5 minute intervals, if configured to do so.)

Both Summer and Winter Shipping Challenge Profiles began at ambient temperature of 20ºC, at which the Medstow Micro took 40 minutes to cool down from ambient to 5ºC. The passive shipper takes over 20 hours to rise from freezing temperatures to 5ºC.

The Styrofoam shipper maintained refrigeration temperatures for approximately 16 hours in the summer profile and 20 hours in the winter profile. Meanwhile, the Medstow Micro maintained lasting refrigeration temperatures for the entire 72-hour duration of both summer and winter profiles.

The Styrofoam shipper remained below 8ºC for up to 35 hours in the summer profile and 53 hours in the winter profile. Comparatively, the Medstow Micro never surpassed 8ºC for either profile.

The Styrofoam shipper gel packs melt (change “phase”) in what is called “passive cooling.” Meanwhile, Artyc’s shippers are designed with built-in temperature sensors for “active cooling”; they utilize batteries to bi-directionally adjust temperature, warming or cooling to stay within a pre-set range. Artyc’s shippers dynamically respond to ambient temperature changes, allowing them to adapt to both summer and winter simulated conditions. Artyc’s Medstow Micro shipper is equipped with an internal thermal sensor, which Labcorp separately validated with a thermocouple. To measure temperature for their Styrofoam shipper, Labcorp used a conventional thermal logger.

Summer Profile

The ambient temperature profile, represented by the gray line, follows a stepped progression that mimics real-world summer shipping conditions. Notably, the ambient temperature ramps up in distinct intervals, peaking twice at approximately 35–37°C—once around the 20-hour mark and again near the end of the test at 70 hours. This level of thermal stress closely mirrors conditions inside non-refrigerated shipping trucks, cargo vans, and warehouse loading areas during the summer, where internal temperatures routinely reach 35–45°C (95–113°F) even when outside air temperatures are significantly cooler. Temperatures inside delivery vehicles can exceed 40°C under typical summer conditions, which is why the U.S. Food and Drug Administration advises stability testing drugs under such high conditions [1]. Between these heat spikes, the ambient temperature drops back to more moderate levels (typically between 15°C and 25°C), simulating the variability encountered in transit environments during summer months.

The passive gel-pack shipper, shown in orange, begins near freezing and takes 21 hours to warm to 5°C. By approximately hour 35, the temperature inside the passive shipper crosses the 8°C upper threshold and continues to rise dramatically. Around the 40-hour mark, it reaches 15°C and tracks ever closer to the ambient profile thereafter, offering little to no insulation from external conditions. This indicates a rapid loss of thermal control, especially under the stress of elevated ambient temperatures. The passive shipper fails to maintain the critical 2–8°C temperature range, which it only maintained for approximately 16 hours.

In contrast, the Artyc Medstow Micro shipper, depicted in blue, demonstrates temperature stability across the full duration of the test. (The initial 12ºC excursion may be attributed to the lid opening, returning to refrigeration within approximately 42 minutes.) The internal temperature remains tightly regulated between 2°C and 8°C, showing no discernible excursions, even during periods when the ambient temperature surges to above 35°C. The Medstow Micro counteracts extreme environmental fluctuations and maintains strict cold chain compliance over the entire 72 hour period. At 72 hours, Labcorp notes more than 40% battery charge remaining on the Micro, which could have continued cooling.

Winter Profile

The ambient temperature profile, shown in gray, features sharp and repeated drops in temperature to as low as -5°C, simulating winter transit conditions inside delivery vehicles, at airport tarmacs, or during cross-docking between regional distribution hubs.

The passive gel-pack shipper, indicated by the orange line, struggles significantly in this profile. Each time the ambient temperature drops, the internal temperature of the passive shipper follows closely — often dipping below freezing. This pattern suggests that the ice packs inside the passive container freeze during cold ambient exposures, which later leads to uncontrolled warming as the ice slowly melts during the warmer portions of the profile. This causes significant temperature swings and prolonged excursions outside the 2–8°C range, with both sub-freezing exposure and excessive warming near the end of the test. This behavior is problematic for temperature-sensitive biologics and blood-based samples, which may suffer irreversible damage from freeze-thaw cycles.

In contrast, the Artyc Medstow Micro shipper, represented by the blue line, demonstrates precise thermal control throughout the full test. Despite the severe external temperature fluctuations, the internal temperature remains tightly regulated within the 2–8°C range, with only minimal, momentary deviations. In fact, the deviations never rise above 7ºC nor drop below 3ºC. The Artyc device dynamically responds to changing ambient conditions, preventing freezing even when the environment drops to sub-zero temperatures. The battery charge of the Micro at 72 hours is not noted.

Discussion

After considering environmental conditions, active cooling solutions may be better equipped to withstand temperature fluctuations than passive solutions.

In both profiles, due to the gel packs, the passive solution started at frozen temperatures. This rapid and dramatic “flash-freeze” at the outset of a shipment may damage sensitive cargo. As a result, passive solutions may require additional protective insulation in packing. Comparatively, the Medstow Micro does not require packing ice packs, nor does it require additional insulation. This maximizes storage space for temperature sensitive cargo.

This study highlights the limitations of passive cooling methods. Their cooling capacities are limited by the duration of their chemical reactions (i.e. melting). Meanwhile, Artyc’s active cooling lasts for as long as it has sufficient battery charge. Limited by their chemical reactions, the passive solutions are effectively irrecoverable once they exceed refrigerated temperatures. In the summer profile, the passive shipper reached a “point of no return” at 35 hours, when it surpassed 8ºC. Due to this limitation, a blood sample shipped with this passive solution may require Priority Overnight shipping. Comparatively, shipping with Artyc’s Medstow Micro would not require this costly, expedited shipping.

Overall, the summer and winter profiles demonstrate that while passive solutions are highly vulnerable to temperature volatility, the Artyc Medstow Micro provides reliable, repeatable protection against the thermal extremes commonly encountered in summertime and wintertime logistics.

This study illustrated:

• Rapid failure of passive shippers as phase change materials when ambient temperatures spiked, exhausted their cooling capacity.

• The Micro’s superior stability, maintaining refrigeration 4.5x longer than passive solutions.

• The Micro’s quick recovery from temperature excursions, showcasing active cooling advantages.

• The Micro eliminating the risk of freeze-thaw cycles, especially in winter shipments.

• The Micro’s simplified packing requirements.

Future Considerations

The Medstow Micro’s inductive cooling system ensures uniform contact with sample tubes, unlike passive shippers, where uneven cooling can compromise sample integrity. Future studies could also explore the impact of surface contact with cooling agents on biological stability.

References

[0] Laboratory Corporation of America Holdings. 2024 Annual Report (Form 10-K). Burlington (NC): Labcorp Holdings Inc.; 2025.

[1] FDA, "Guidance for Industry: Q1A (R2) Stability Testing of New Drug Substances and Products,” 2003.

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