RNA quality analysis. A) Microcapillary electrophoresis patterns of total RNA extracted from fecal samples of one individual that underwent 12 different storage conditions: immediately frozen at −20°C (F); immediately frozen and then unfrozen (UF) during 1 h and 3 h; kept at room temperature (RT) during 3 h, 24 h, 48 h, 72 h and 2 weeks; mixed with commercial RNAse inhibitor solution (RNA later) and kept at room temperature during 3 h, 24 h, 2 weeks and 4 weeks. The equivalent to 1 mg of fecal material is loaded on each lane. A RNA fragment size (nt) marker was loaded in the first lane from the left side. B) Summary plot of average RNA integrity numbers (RIN) obtained with samples stored in the above 12 conditions. N = 11 individuals for the 88 samples stored without RNAse inhibitor. Standard deviation is indicated for each storage condition. N = 6 individuals for the 24 samples stored with RNAse inhibitor. Statistical analysis was performed using Poisson regression model (the star (*) means that the comparison with the frozen sample RIN number was significant with p < 0.05).