Fit for purpose frozen tissue collections by RNA integrity number-based quality control assurance at the Erasmus MC tissue bank

About 5000 frozen tissue samples are collected each year by the Erasmus Medical Center tissue bank. Two percent of these samples are randomly selected annually for RNA isolation and RNA Integrity Number (RIN) measurement. A similar quality assessment was conducted during centralization of a 20-year-old tissue collection from the cancer institute, a 15-year-old liver sample archive (-80°C), and a 13-year-old clinical pathology frozen biopsy archive (Liquid Nitrogen). Samples were divided into either high-quality (RIN ≥6.5) or low-quality overall categories, or into four "fit-for-purpose" quality groups: RIN <5: not reliable for demanding downstream analysis; 5 ≤RIN <6: suitable for RT-qPCR; 6 ≤RIN <8: suitable for gene array analysis; and RIN ≥8: suitable for all downstream techniques. In general, low RIN values were correlated with fatty, fibrous, pancreatic, or necrotic tissue. When the percentage of samples with RIN ≥6.5 is higher than 90%, the tissue bank performance is adequate. The annual 2011 quality control assessment showed that 90.3% (n=93) of all samples had acceptable RIN values; 97.4% (n=39) of the cancer institute collection had RIN values above 6.5; and 88.6% (n=123) of samples from the liver sample archive collection had RIN values higher than 6.5. As the clinical pathology biopsy collection contained only 58.8% (n=24) acceptable samples, the procurement protocols used for these samples needed immediate evaluation. When the distribution of RIN values of the different collections were compared, no significant differences were found, despite differences in average storage time and temperature. According to the principle of "fit-for-purpose" distribution, the vast majority of samples are considered good enough for most downstream techniques. In conclusion, an annual tissue bank quality control procedure provides useful information on tissue sample quality and sheds light on where and if improvements need to be made.

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