Associations between hemostatic markers and mortality in COVID-19 - Compounding effects of D-dimer, antithrombin and PAP complex

Abstract

In this single-center cohort study, we applied a panel of laboratory markers to characterize hemostatic function in 217 consecutive patients that underwent testing for COVID-19 as they were admitted to Linköping University Hospital between April and June 2020. In the 96 patients that tested positive for SARS-CoV-2 (COVID-19+), the cumulative incidences of death and venous thromboembolism were 24.0% and 19.8% as compared to 12.4% (p = 0.031) and 11.6% (p = 0.13) in the 121 patients that tested negative (COVID-19-). In COVID-19+ patients, we found pronounced increases in plasma levels of von Willebrand factor (vWF) and fibrinogen. Excess mortality was observed in COVID-19+ patients with the following aberrations in hemostatic markers: high D-dimer, low antithrombin or low plasmin-antiplasmin complex (PAP) formation, with Odds Ratios (OR) for death of 4.7 (95% confidence interval (CI95) 1.7-12.9; p = 0.003) for D-dimer >0.5 mg/L, 5.9 (CI95 1.8-19.7; p = 0.004) for antithrombin (AT) ˂0.85 kIU/l and 4.9 (CI95 1.3-18.3; p = 0.019) for PAP < 1000 μg/L. Compounding increases in mortality was observed in COVID-19+ patients with combined defects in markers of fibrinolysis and coagulation, with ORs for death of 15.7 (CI95 4.3-57; p < 0.001) for patients with PAP <1000 μg/L and D-dimer >0.5 mg/L and 15.5 (CI95 2.8-87, p = 0.002) for patients with PAP <1000 μg/L and AT ˂0.85 kIU/L. We observed an elevated fraction of incompletely degraded D-dimer fragments in COVID-19+ patients with low PAP, indicating impaired fibrinolytic breakdown of cross-linked fibrin.

Keywords: Antithrombin; COVID-19; Fibrinolysis; Plasmin-antiplasmin complex.

Graphical abstract

Fig. 1

Association of clinical and laboratory parameters with mortality in COVID-19+ patients. Univariate analysis of Odds Ratios for death in COVID-19+ patient subgroups. COVID-19+ patients were dichotomized according to (A) clinical or (B) laboratory parameters. Abbreviations: OR = Odds Ratio, CI = Confidence Interval, IHD = Ischemic heart disease, BMI = Body Mass Index, HFNO = High Flow Nasal Oxygen, CRP = C-reactive Protein.

Fig. 2

Distribution of test results in COVID-19+ and COVID-19− patients at hospital admission.*P < 0.05; **P < 0.01; ***P < 0.001; not significant (n.s.).

Fig. 3

Low PAP and high D-dimer at hospital admission in COVID-19 patients who died during follow-up. Distribution of PAP (A & C) and D-dimer (B) at admission in the following patient subgroups: all COVID-19− patients, all COVID-19+ patients, COVID-19+ patients that were still alive at follow-up, and COVID-19+ patients who died during the follow-up period. In (C) only results from patients with D-dimer levels >0.5 mg/L at baseline are included. Boxes indicate the interquartile range with vertical lines denoting median test results. COVID-19 status is indicated with “−” or “+”. *P < 0.05; **P < 0.01; ***P < 0.001; not significant (n.s.).

Fig. 4

Levels of D-Dimer in COVID-19+ patients. Western blotting analysis of D-dimer fragments in plasma samples of COVID-19+ patients. Equal volume of plasma was loaded onto each lane. (A) The D-dimer standard band at 180kDA is indicated by arrow and the corresponding bands in patients with low and high PAP is indicated by arrowhead. (B) Quantification of intensity ratios of the 250kDA/180 kDa band in patients with low and high PAP (+SEM). n = 4 for each group. The difference between groups is not significant.