Of all the factors that must be considered when transporting samples, temperature is one of the most important. From blood and human serum to soil and plant matter, temperature can affect both the physical and chemical stability of specimens. Once the integrity of a sample has been compromised it’s no longer suitable for analysis and can’t offer reliable results.

So, what’s the right temperature for transporting samples? There’s no one-size-fits-all answer as optimal transport temperatures can vary significantly depending on the sample. That said, there are benchmark recommendations for common sample types:

Transport temperatures for blood samples
Most laboratories recommend storing and transporting blood samples at temperatures of between 4°C and 25°C. Ideally, specimens should arrive at the laboratory within three to four days to ensure biomarker concentrations aren’t altered.

While dry ice is the preferred method of transport when moving blood samples between hospitals and testing laboratories, studies suggest gel packs can be just as effective. A recent article published in the journal Shock maintains gel packs are a cost-effective way to maintain temperatures of 4°C and preserve the integrity of “inflammatory, coagulation, endothelial dysfunction, and oxidative stress biomarkers”.

Transport temperatures for serum
Most serum samples can be transported at temperatures of between 2°C and 8°C, provided they reach the testing laboratory within one week. Refrigerated transport is ideal though dry ice can also be used. For longer periods of time the recommended temperature for storing serum samples is -20°C.

Transport temperatures for water
Water collected for bacteriology testing should be transported at temperatures of around 4°C. Anything higher or lower could compromise the integrity of the sample and risk killing bacteria.

Transport temperatures for chemical testing
4°C is also the recommended temperature for transporting samples that will undergo chemical testing.

Transport temperatures for infectious samples
As well as adhering to specialised health and safety regulations, it’s important to consider temperature when transporting infectious samples. For example, the Centers for Disease Control and Prevention (CDC) recommends the following guidelines when transporting respiratory specimens, including COVID-19 tests:

“Store respiratory specimens at 2-8°C for up to 72 hours after collection. If a delay in testing or shipping is expected, store specimens at -70°C or below. Store extracted nucleic acid samples at -70°C or lower.”