Immunothrombosis and plasma fibrinolytic function for pediatric COVID-19: a secondary analysis from the COVAC-TP trial

Abstract

The relationship between fibrinolysis, inflammation, and prothrombotic risk among children hospitalized for coronavirus disease 2019 (COVID-19)-related illness is ill defined. To investigate the association between plasma fibrinolytic capacity and proinflammatory cytokine concentrations among children hospitalized for primary COVID-19 infection and multisystem inflammatory syndrome in children (MIS-C), we hypothesized that cytokine concentrations differ by clinical phenotype and are associated with hypofibrinolysis. We analyzed banked plasma specimens serially collected from children aged <18 years admitted for primary COVID-19 or MIS-C and enrolled in the COVID-19 Anticoagulation in Children-Thromboprophylaxis multicenter trial, an open-label, multicenter, phase 2 clinical trial conducted between July 2020 and May 2021. Plasma coagulative and fibrinolytic function were measured via the clot formation and lysis (CloFAL) assay and modified mini-euglobulin clot lysis assay (ECLA). Interleukin-1β (IL-1β), IL-6, and IL-8, and tumor necrosis factor α were measured by the Meso Scale Discovery assay. Correlations were evaluated using Spearman rank testing. A total of 132 banked plasma specimens from 38 participants (COVID-19: n = 18; MIS-C: n = 20) were analyzed. Overall, increased coagulative function (ie, elevated CloFAL area under the curve) and impaired fibrinolytic function (ie, reduced CloFAL fibrinolytic index [FI] and elevated modified mini-ECLA clot lysis time ratio [CLTR]) were observed but most notably among those with MIS-C. Plasma cytokine concentrations correlated with assay indices of hypofibrinolysis (ie, modified mini-ECLA CLTR and CloFAL FI). In summary, among children hospitalized for COVID-19-related illness, hypercoagulability and hypofibrinolysis are mediated, in part, by inflammation that may contribute to prothrombotic risk. This trial was registered at www.ClinicalTrials.gov as #NCT04354155.

Graphical abstract

Figure 1.

Box and whisker plot of CloFAL AUC for participants of the COVAC-TP trial with COVID-19 and MIS-C. The P values presented below plots for each day represent comparisons of values between those with COVID-19 and MIS-C. The P values with brackets above the plots represent comparison of pooled values for each day as compared with day 0. Total samples analyzed by study time point are as follows: day 0 (n = 20), day 1 (n = 24), day 2 (n = 19), day 3 (n = 17), day 7 (n = 8), and day 14 (n = 4).

Figure 2.

Box and whisker plot of modified mini-ECLA CLTR for participants of the COVAC-TP trial with COVID-19 and MIS-C. The P values presented below plots for each day represent comparisons of values between those with COVID-19 and MIS-C. The P values with brackets above the plots represent comparison of pooled values for each day as compared with day 0. Total samples analyzed by study time point are as follows: day 0 (n = 26), day 1 (n = 35), day 2 (n = 28), day 3 (n = 29), day 7 (n = 10), and day 14 (n = 4).

Figure 3.

Box and whisker plot of CloFAL FI for participants of the COVAC-TP trial with COVID-19 and MIS-C. The P values presented below plots for each day represent comparisons of values between those with COVID-19 and MIS-C. The P values with brackets above the plots represent comparison of pooled values for each day as compared with day 0. Total samples analyzed by study time point are as follows: day 0 (n = 20), day 1 (n = 24), day 2 (n = 19), day 3 (n = 17), day 7 (n = 8), and day 14 (n = 4).

Figure 4.

Proinflammatory cytokine concentrations among children hospitalized with COVID-19 and MIS-C enrolled into the COVAC-TP trial. Concentrations are depicted below as median with IQR. Total samples analyzed by study time point are as follows: day 0 (n = 28), day 1 (n = 35), day 2 (n = 28), day 3 (n = 28), day 7 (n = 11), and day 14 (n = 5).

Figure 5.

Spearman rank correlation heat map between plasma CloFAL indices and proinflammatory cytokines concentrations among children hospitalized with COVID-19 and MIS-C enrolled into the COVAC-TP trial. AOC, area over the curve; CI, coagulation index; T1, time to MA.

Figure 6.

Spearman rank correlation heat map between plasma modified mini-ECLA indices and proinflammatory cytokine concentrations among children hospitalized with COVID-19 and MIS-C enrolled into the COVAC-TP trial. AUCR, area under the curve ratio; DODR, delta optic density ratio.