Data from: Making it last: storage time and temperature have differential impacts on metabolite profiles of airway samples from cystic fibrosis patients

Metabolites of human or microbial origin have the potential to be important biomarkers of disease state in cystic fibrosis (CF). Clinical sample collection and storage conditions may impact metabolite abundances with clinical relevance. We measured the change in metabolite composition based on untargeted gas chromatography mass spectrometry (GC-MS) when CF sputum samples were stored at either 4°C, -20°C, or -80°C with one or two freeze-thaw cycles. Daily time points were taken for one week and then weekly for 4 weeks (4°C) and 8 weeks (-20°C). The metabolites in samples stored at -20°C maintained similar abundances compared to -80°C over the course of eight weeks (average change in Bray-Curtis distance: 0.06±0.04), and were also stable after one or two freeze-thaw cycles. However, metabolite profiles of samples stored at 4°C shifted after one day and continued to change over the course of four weeks (average change in Bray-Curtis distance: 0.31±0.12). Several amino acids and other metabolite abundances increased with time when stored at 4°C, but remained constant at -20°C. Storage temperature was a significant factor driving the metabolite composition (PERMANOVA R2 = 0.32 to 0.49, p= <0.001). CF sputum samples stored at -20°C at the time of sampling maintain a relatively stable untargeted GC-MS profile. Samples should be frozen on the day of collection, as more than one day at 4°C impacts the global composition of the metabolites in the sample.

人类或微生物来源的代谢物，有望成为囊性纤维化（Cystic Fibrosis, CF）患者疾病状态的重要生物标志物。临床样本的采集与储存条件，可能会影响具有临床相关性的代谢物丰度。本研究采用非靶向气相色谱-质谱联用技术（untargeted gas chromatography mass spectrometry, GC-MS），分析了囊性纤维化痰液样本在4℃、-20℃或-80℃条件下，经1次或2次冻融循环后的代谢物组成变化。在4℃储存组中，我们于1周内每日采样，随后4周内每周采样；在-20℃储存组中则持续采样至8周。在8周的储存周期内，-20℃储存样本的代谢物丰度与-80℃组保持相近水平（布雷-柯蒂斯距离（Bray-Curtis distance）平均变化量：0.06±0.04），且经1次或2次冻融循环后仍保持稳定。但4℃储存的样本，其代谢物谱在1天后即发生偏移，并在4周内持续变化（布雷-柯蒂斯距离平均变化量：0.31±0.12）。在4℃储存条件下，部分氨基酸及其他代谢物的丰度随储存时间延长而升高，而在-20℃条件下则保持恒定。储存温度是驱动代谢物组成差异的显著因素（置换多元方差分析（Permutational Multivariate Analysis of Variance, PERMANOVA）R²=0.32~0.49，p<0.001）。采集后即刻于-20℃储存的囊性纤维化痰液样本，其非靶向气相色谱-质谱联用谱图相对稳定。建议样本于采集当日即进行冻存，因为在4℃放置超过1天，会对样本内代谢物的整体组成产生影响。