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. 2021 Jun 9;1(2):74–85. doi: 10.1097/ID9.0000000000000010

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Copyright © 2021 The Chinese Medical Association, published by Wolters Kluwer Health, Inc.

This is an open access article distributed under the terms of the Creative Commons Attribution-Non Commercial-No Derivatives License 4.0 (CCBY-NC-ND), where it is permissible to download and share the work provided it is properly cited. The work cannot be changed in any way or used commercially without permission from the journal. http://creativecommons.org/licenses/by-nc-nd/4.0

This article is made available via the PMC Open Access Subset for unrestricted re-use and analyses in any form or by any means with acknowledgement of the original source. These permissions are granted for the duration of the COVID-19 pandemic or until permissions are revoked in writing. Upon expiration of these permissions, PMC is granted a perpetual license to make this article available via PMC and Europe PMC, consistent with existing copyright protections.

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Global metabolic perturbation in COVID-19 patients compared with healthy controls. (A) The principal component analysis shows the overall distribution pattern in plasma metabolites in healthy controls and COVID-19 patients. The first and second components from the principal component analysis explained 18.11% and 12.63% total variance. Concentration ellipses are at a 95% level based on a multivariate normal distribution. (B) The OPLSDA analysis shows the classification of healthy controls and COVID-19 patients based on the annotated metabolites, where predictive component (t1) and first orthogonal component (o1) explain 10% and 14% total variance in X (X: metabolomics data, Y: class label). pR2Y and pQ2 were derived from repeated permutations (20 times) with 5-fold cross-validation. (C) The hierarchical clustering analysis using all the annotated metabolites. (D) The volcano plot shows log₂ fold change (based on original peak area) and FDR (cut-off at 0.05) based on Welch t-test P-values of the annotated metabolite. (E) The barplot shows the enrichment fold for metabolite sets with more than 2 hits in increasing order of P-value from top to bottom. The P-values are indicated in each bar. The numbers of identified metabolites in each metabolite set that are statistically significant (FDR < 0.05) and not significant are shown (F). COVID-19: coronavirus disease 2019; OPLSDA: orthogonal partial least square discriminant analysis; FDR: false discovery rate.