Correlation between the RIN value and Pearson correlation. In order to evaluate the RIN cut-off value of 6, we compared it to Pearson correlation coefficients. Pearson correlation coefficients were obtained, when the gene expression levels of the samples for the different time periods at room temperature, were related to the gene expression levels of the samples left 50 seconds at room temperature. If the correlation coefficient of the gene expression level is the true value, two samples obtain unexpected RIN values, i.e. a low correlation coefficient and a RIN value above the cut-off or vice versa (arrows, RIN 5 = Sample 5, 10 min and RIN 6 = Sample 3, 30 min).