How should we store the urine samples?
Normally biological samples are stored at -80°C to maintain the samples biologically and physiologically representative. It is well-known that there might be some minor and/or molecule-specific changes in biological samples, if they have been stored, e.g., at -20°C for prolonged times.
However, these changes can be minor and thus irrelevant for your study. We can of course also analyse samples that have been stored at lower temperatures, however, please note that there may be some deviations in the overall biomarker concentrations compared to if the sample had been stored at -80°C.
How long can the samples be stored?
Some publications exist that report minor effects of long-term storage on urine samples. There are next to no changes at -80°C, but more significant changes start to occur at higher temperatures. However, these changes are still much less significant than with blood samples.