Because the value of biobanks depends on the quality of samples housed there, a new study, published in Clinical Biochemistry, investigated the long-term stability of 10 analytes, including cholesterol, low- and high-density cholesterol (HDL-C), and hormones such as follicle stimulating hormone and free thyroxin.
The specimens—taken from 520 men ages 40 to 49 and kept for 0, 4, 17, and 29 years, respectively—were stored at -25 °C. The fresh samples were used for reference to calculate how samples changed.
All of the lipids and apolipoproteins changed over time except for total cholesterol, while most of the hormones remained stable, and prolactin showed signs it had degraded. In comparison to newly taken samples, the mean values of those stored 29 years were 12% higher for apolipoprotein A1, 22.3% higher for apolipoprotein B, and 69.2% lower for HDL-C.
While interesting, the study did not have ideal conditions for assessing sample stability. “Is this the perfect protocol to assess long term analyte stability? No—certainly not, as the authors note in their discussion,” wrote Catherine A. Hammett-Stabler, PhD, DABCC, FACB, in an accompanying editorial. “Changes in the population in terms of habits (exercise, smoking, diet, etc.) or environment must be considered as such are beyond the control of any protocol and easily confound studies. In addition, as we know, collection, preparation, and storage conditions appropriate for one analyte may not be valid for another. Furthermore, as others have demonstrated in sample stability studies, there is variation in the rate of change between individuals observed for most analytes.”
Still, this study and other similar research are good efforts to start determining the best conditions for storage. “Realistically speaking, it is likely that no single protocol to assess sample quality and/or analyte stability will meet the needs of all banks, investigators, or studies,” wrote Hammett-Stabler.