TABLE 2.
Features selected by orthogonal partial least squares-discriminant analysis (OPLS-DA) analysis and in principal components analysis (PCA-X) model with their CAS numbers
| Feature number/CAS number | OPLS-DA | PCA-X | tr (min)/top 3 m/z |
| 1 (↑) | Feature 1 | Feature 1 | 4.21/41, 55, 56 |
| 2 /590-36-3 (↑) | 2_Pentanol_2_methyl | 2_Pentanol_2_methyl | 9.14/59, 45, 87 |
| 3 /100-52-7 (↑) | Benzaldehyde# | Benzaldehyde#, ¶ | 16.9/105, 77, 106 |
| 4 (↓) | Feature 4 | Feature 4 | 21.5/119, 91, 148 |
| 5 /565-75-3 (↑) | Pentane_2_3_4_trimethyl | Pentane_2_3_4_trimethyl | 10.1/43, 70, 71 |
| 6 /629-94-7 (↓) | Heneicosane | Heneicosane | 46.98/57, 71, 43 |
| 7 (↑) | Feature 7 | Feature 7 | 13.19/69, 111, 55 |
| 8 (↑) | Feature 8 | Feature 8 | 31.5/83, 82, 55 |
| 9 (↓) | Feature 9 | Feature 9¶ | 46.2/236, 193, 167 |
| 10 | Feature 10 | 20.56/56, 55, 42 | |
| 11 /64-19-7 | Acetic acid# | 6.09/45, 43, 60 | |
| 12 /64-17-5 | Ethanol# | 4.45/45, 46,43 | |
| 13 /592-27-8 | Heptane-2-methyl# | 12.6/43, 57, 42 |
Features with given names that were identified using the National Institute of Standards and Technology library and achieved a high match factor of >800 are highlighted in bold. Arrow highlights direction of the concentration change in COVID-19 positive participants. tr: retention time; m/z: mass to charge ratio of main ions. #: volatile organic compounds identified to level 1 of metabolic standard recommendations. ¶: features with statistically significant (p<0.05) differences in levels between SARS-CoV-2 positive and negative samples, as determined in an independent sample t-test.