Peak Plasma Levels of mtDNA Serve as a Predictive Biomarker for COVID-19 in-Hospital Mortality

Abstract

Several predictive biomarkers for coronavirus disease (COVID-19)-associated mortality in critically ill patients have been described. Although mitochondrial DNA (mtDNA) is elevated in patients with COVID-19, the association with coagulation function and its predictive power for mortality is unclear. Accordingly, this study investigates the predictive power of mtDNA for in-hospital mortality in critically ill patients with COVID-19, and whether combining it with thromboelastographic parameters can increase its predictive performance. This prospective explorative study included 29 patients with COVID-19 and 29 healthy matched controls. mtDNA encoding for NADH dehydrogenase 1 (ND1) was quantified using a quantitative polymerase chain reaction analysis, while coagulation function was evaluated using thromboelastometry and impedance aggregometry. Receiver operating characteristic (ROC) curves were used for the prediction of in-hospital mortality. Within the first 24 h, the plasma levels of mtDNA peaked significantly (controls: 65 (28-119) copies/µL; patients: 281 (110-805) at t₀, 403 (168-1937) at t₂₄, and 467 (188-952) copies/µL at t₇₂; controls vs. patients: p = 0.02 at t₀, p = 0.03 at t₂₄, and p = 0.44 at t₇₂). The mtDNA levels at t₂₄ showed an excellent predictive performance for in-hospital mortality (area under the ROC curve: 0.90 (0.75-0.90)), which could not be improved by the combination with thromboelastometric or aggregometric parameters. Critically ill patients with COVID-19 present an early increase in the plasma levels of ND1 mtDNA, lasting over 24 h. They also show impairments in platelet function and fibrinolysis, as well as hypercoagulability, but these do not correlate with the plasma levels of fibrinogen. The peak plasma levels of mtDNA can be used as a predictive biomarker for in-hospital mortality; however, the combination with coagulation parameters does not improve the predictive validity.

Keywords: SARS-CoV2; biomarker; immunothrombosis; intensive care unit; nucleic acids.

Figure 1

Quantification of ND1 mtDNA. (A): Significantly elevated levels of ND1 mtDNA were found in patients with COVID-19 compared with those in matched healthy controls. (B): Elevated levels of ND1 mtDNA were found in the COVID-19 patients after admission to the intensive care unit (t₀) and 24 h thereafter (t₂₄), compared with those in the controls. An analysis of the different time points among the COVID-19 patients revealed no significant differences. Asterisks display the degree of statistical significance: *: p ≤ 0.05, ***: p < 0.001. Abbreviations: COVID-19 = coronavirus disease; CTRL = control group; mtDNA = mitochondrial DNA; ND1 = NADH dehydrogenase 1.

Figure 2

Time course of impedance platelet aggregometry. Patients with COVID-19 presented significantly unsatisfactory AUCs for the ASPI level at t₀ and the ADP level at t₂₄. No significant differences in the TRAP level were found. Asterisks display the degree of statistical significance: *: p ≤ 0.05. Abbreviations: ADP = adenosine diphosphate; ASPI = arachidonic acid; AUC = area under the curve; CTRL = control group; TRAP = thrombin receptor-activating peptide.

Figure 3

Time course of thromboelastometry. Patients with COVID-19 presented a significantly increased MCF at 72 h (EXTEM (A) and INTEM (B) assays) and 24 h (INTEM (B)) after admission to the ICU compared with the controls. In the FIBTEM assay (C), the MCF increased in patients with COVID-19 at all time points compared with that in the controls. No differences were found in the APTEM assay (D). Asterisks display the degree of statistical significance: *: p ≤ 0.05, **: p < 0.01. Abbreviations: APTEM = aprotinin-based thromboelastometry; CTRL = control group; EXTEM = extrinsically activated thromboelastometry; FIBTEM = fibrinogen-based thromboelastometry; INTEM = intrinsically activated thromboelastometry; MCF = maximum clot firmness.

Figure 4

Prediction of in-hospital mortality. The receiver operating characteristic curves for the mtDNA level, FIBTEM MCF × mtDNA level, EXTEM MCF × mtDNA level and TRAP × mtDNA level are shown. The curves are presented for each time point (t₀, t₂₄ and t₇₂) individually, as well as for all time points. Abbreviations: EX.MCF = maximum clot firmness in the extrinsically activated thromboelastometry assay; FI.MCF = maximum clot firmness in the fibrinogen-based thromboelastometry assay; mtDNA = mitochondrial DNA; TRAP = thrombin receptor-activating peptide.

Figure 5

Prediction of in-hospital mortality in ARDS subgroups. The receiver operating characteristic curves are shown for the mtDNA levels, divided into ARDS-groups (no/mild and moderate/severe). The curves are presented for each time point (t₀, t₂₄ and t₇₂) individually, as well as for all timepoints. Abbreviations: ARDS = acute respiratory distress syndrome.