Background: Liquid biobanking is an important tool for laboratory diagnostics in routine settings and clinical studies. However, the current knowledge about adequate storage conditions for different classes of biomarkers is incomplete and, in part, contradictory. Here, we performed a comprehensive study on the effects of different storage conditions on the stability of various biomarkers in human serum and plasma.
Methods: Serum and citrated plasma were aliquoted and stored at 4 °C, -20 °C, -80 °C, and <-130 °C for 0, 7, 30, and 90 days, respectively (5-10 pools/condition). Additionally, frozen aliquots were temporarily exposed to higher temperatures during storage to simulate removing individual samples. Stability was tested for 32 biomarkers from 10 different parameter classes (electrolytes, enzymes, metabolites, inert proteins, complement factors, ketone bodies, hormones, cytokines, coagulation factors, and sterols).
Results: Biobanking at -80 °C and <-130 °C for up to 90 days did not lead to substantial changes (defined as >3 interassay coefficients of variation and p<0.01) of any biomarker concentration. In contrast, storage at 4 °C and -20 °C induced substantial changes in single biomarker concentrations in most classes. Such substantial changes were increases (<20%) in electrolytes, metabolites, and proteins, and decreases (<96%) in enzymes, ketone bodies, cytokines, and coagulation factors. Biomarker stability was minimally affected by occasional short-term thermal exposure.
Conclusions: Based on these results, we provide recommendations for storage conditions of up to 90 days for several biomarkers. Generally, storage at ≤-80 °C for at least 90 days including occasional short-term thermal exposure is an excellent storage condition for most biomarkers.