Aims To establish whether RNA degrades in long-term storage at −80°C and whether RNA integrity numbers (RINs) determine ‘fitness for purpose’ in severely degraded RNA.
Methods RNA was extracted from 549 thyroid biospecimens stored at −80°C for 0.1–10.9 years then their RINs correlated with storage time. RT-PCR for 65, 265, 534 and 942 base pair amplicons of hydroxymethylbilane synthase was used to measure amplicon length in RNA from cryopreserved and FFPE biospecimens that were equally degraded according to RIN.
Results Storage time did not correlate with RIN. Longer amplicons were obtained from cryopreserved samples than FFPE samples with equal RINs.
Conclusions RNA does not degrade in thyroid biospecimens stored for long periods of time at −80°C. Although RINs are known to predict amenability to analytical platforms in good quality samples, this prediction is unreliable in severely degraded samples.
- BIOLOGICAL SCIENCES
- THYROID CANCER
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Handling editor Cheok Soon Lee
Contributors WM carried out some of the RNA extractions and RIN analysis, did all the size RT-PCR work, compiled all of the data, did the statistical analyses and wrote the manuscript. The remaining authors, with the exception of GAT and FB did the remaining RNA extractions and RIN analyses. FB provided financial assistance for the writing of the manuscript and significant intellectual input into the manuscript. GAT has overall control of the Chernobyl Tissue Bank, had the idea for the paper and provided significant intellectual input into the manuscript.
Competing interests None declared.
Ethics approval Imperial College London Ethics Committee.
Provenance and peer review Not commissioned; externally peer reviewed.