PROTEOMIC ANALYSIS OF EXHALED BREATH CONDENSATE SAMPLES: HIGH REPRODUCIBILITY OF MASS SPECTROMETRIC MEASUREMENTS

Exhaled breath condensate is considered a rich source of biomarkers that can provide valuable information for early diagnosis of respiratory and systemic diseases. However, exhaled breath condensate (EBC) consists mainly of water vapor and the concentration of analytes in the exhaled breath condensate sample is very low, close to the detection limit of sensitive methods such as mass spectrometry. Here, we have developed a mass spectrometry-based approach to characterize the EBC proteome. We compared biological and technical replicates of the measured samples, compared the protein profile between individual samples of healthy individuals and described the reproducibility between the three technical replicates of the sample taken. We have found that repeated measurements of samples are reproducible and can increase the number of proteins identified. Analysis led to the detection of 2797 unique proteins in all samples. Based on statistical analysis, it was shown that the 10% difference from the mean is due more to the deviation of the mass spectrometry measurements than to the biological variability of the samples. And second, the change in protein amount below 20% of the average in the case of EBC is due to method variability and should not be considered a significant change in protein expression using label-free mass spectrometry techniques. Full text English translation available in the on-line version.