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Flowchart and study design schematic. Sputum samples from two patients were homogenized, aliquoted, and stored at either −20°C or 4°C. Duplicates of stored samples were taken daily for a week, and weekly samples were taken for 4 weeks at 4°C and 8 weeks at −20°C. At each time point, an additional replicate was subjected to either one or two freeze-thaw cycles. The aliquots were all analyzed by untargeted GC-MS.
