Severe winter temperatures can pose a significant risk to diagnostic specimens during transit. Exposure to extreme cold may cause specimens to freeze, compromising sample integrity and potentially delaying or preventing testing. To ensure specimens arrive at the Wisconsin Veterinary Diagnostic Laboratory (WVDL) in acceptable condition, please follow the guidance below when shipping during periods of extreme cold.
Recommended Cold Weather Shipping Practices
Use an Insulated Shipping Container
During extreme cold, specimens should always be shipped in an insulated container, such as a polystyrene cooler placed inside a sturdy cardboard box. Insulation provides critical protection against rapid temperature drops while in transit.
Include Room-Temperature Cold Packs (Not Frozen)
To help buffer temperature fluctuations:
- Use room-temperature cold packs
- Do not use frozen cold packs, as they can promote freezing of specimens
- Separate cold packs from specimens using cardboard, bubble wrap, or other padding material
Cold packs function as thermal mass to stabilize internal temperatures without exposing samples to freezing conditions.
Center and Cushion Specimens
Specimens should be:
- Placed in the center of the insulated container
- Surrounded on all sides with padding
- Kept away from container walls whenever possible
Proper positioning minimizes direct exposure to external cold temperatures.
Double Bag All Specimens
All specimens must be securely double bagged to:
- Prevent leaks if containers crack or lids loosen due to cold temperatures
- Protect paperwork and external packaging
- Meet biological shipping best practices
Cold temperatures can make plastic brittle, increasing the importance of leak-proof packaging and double containment.
Special Guidance for Serum Samples
During cold weather shipping:
- Centrifuge blood tubes and submit serum separated from the clot whenever possible
- Transporting serum off the clot reduces the risk of hemolysis, analyte instability, and freeze-related damage
- Ensure serum is transferred to a leak-proof, properly labeled tube prior to shipment
Separating serum before shipment improves sample stability and helps preserve diagnostic quality during temperature extremes.
Special Guidance for Formalin-Fixed Tissues
During winter and freezing conditions:
- Add 1-part isopropyl alcohol to formalin when submitting tissue samples
- This helps prevent freezing of formalin-fixed tissues during shipment
- Maintain proper fixation volume to preserve sample quality
This step is especially important when overnight temperatures are expected to fall below freezing.
Plan Transit Time Carefully
Weather-related shipping delays increase the risk of specimen freezing. When possible:
- Ship early in the week
- Use overnight or priority delivery services for critical specimens
- Consider delaying shipment during severe weather if specimen stability allows
Monitoring weather forecasts and courier schedules can help minimize cold exposure.
Questions? Contact WVDL Before Shipping
If you are uncertain about specimen stability, packaging methods, or whether to delay shipment during extreme cold, please contact WVDL before sending samples. Our staff are happy to provide guidance to help protect your specimens and avoid the need for resubmission.
You can use our Shipping Program to ensure the most efficient and economical way to ship to WVDL!
