Fibrinolytic parameters in children with noncatheter thrombosis: a pilot study:

Biomarkers in pediatric venous thromboembolism: a systematic review of the literature

BACKGROUND

Accurate prediction of the individual risk of venous thromboembolism (VTE) remains suboptimal in children, and biomarkers are currently not used to stratify the risk of VTE in children.

OBJECTIVES

This study aimed to assess which biological or radiological biomarkers may predict VTE or VTE complications in children.

PATIENTS/METHODS

A literature search was performed for peer-reviewed publications (1990-2022). We included studies addressing the use of biomarkers for patients aged 29 days to 18 years to predict VTE or its complications, including but not limited to TE-related death, VTE recurrence, or postthrombotic syndrome. Given the heterogeneity of the study designs, populations, and outcomes, no quantitative data synthesis was performed.

RESULTS

Forty studies were included, totaling 10,987 participants (median age: 4.7 years). Reports were often lacking critical methodological data, including blood collection method (68% of studies) and timepoints, laboratory testing technique (41%), or primary outcome definition (20%). Forty-six individual biomarkers were assessed for VTE prediction (32 studies, 9525 participants), including d-dimers, fibrinogen, platelet count, white blood cell count, and factor VIII. Albumin, C-reactive protein, d-dimers, factor VIII, and thrombin-antithrombin levels showed promising results for VTE prediction. In 9 studies (1606 participants), no biomarker was consistently predictive of postthrombotic syndrome, VTE persistence, or VTE recurrence in children.

CONCLUSIONS

Several candidate biomarkers were promising in the prediction of VTE in children. Still, discrepancies between different studies and the high risk of bias from the current literature prevent their widespread use in the clinical setting. Further prospective research in various pediatric subpopulations is required.

Plasmatic coagulation and fibrinolysis in healthy and Otostrongylus-affected Northern elephant seals (Mirounga angustirostris)

BACKGROUND

Prepatent Otostrongylus arteritis results in hemorrhagic diathesis in free-ranging Northern elephant seals (Mirounga angustirostris) attributed to aberrant larval migration of the lungworm, Otostrongylus circumlitus. Clinical signs are often nonspecific, including lethargy, anorexia, and blepharospasm, but can progress to spontaneous frank hemorrhage and death within 72 hours of onset. Previously published case reports describe coagulopathy with prolonged PT and APTT, normal to elevated platelet counts, normal antithrombin concentrations, and low concentrations of fibrinogen degradation products. Disseminated intravascular coagulation was proposed as the cause of hemorrhage, but is inconsistent with some of the reported clinicopathologic changes.

OBJECTIVE

The purpose of this study was to compare plasmatic coagulation and fibrinolysis in healthy and Otostrongylus-affected elephant seals, in order to identify potential therapy. We hypothesized that hyperfibrinolysis contributed to hemorrhage in these cases.

METHODS

Citrated plasma samples were collected from 3- to 4-month-old Northern elephant seals in a wildlife rehabilitation hospital. The sampled population included 25 healthy, prerelease seals and 32 clinically ill seals diagnosed with presumptive Otostrongylus arteritis. Twenty-one of the included seals had Otostrongylus infestation confirmed at necropsy. Standard coagulation tests and plasma thromboelastography were performed for a complete assessment of coagulation and fibrinolysis.

RESULTS

Northern elephant seals with definitive Otostrongylus infestation were hypocoagulable and hypofibrinolytic compared to healthy controls.

CONCLUSIONS

Results were most consistent with disseminated intravascular coagulation. Treatment with antifibrinolytic drugs to control hemorrhage may be unrewarding; alternative therapies such as plasma transfusions or coagulation factor concentrates should be investigated.

Evaluation of tranexamic acid and ε-aminocaproic acid concentrations required to inhibit fibrinolysis in plasma of dogs and humans

OBJECTIVE

To determine minimum plasma concentrations of the antifibrinolytic agents tranexamic acid (TEA) and ε-aminocaproic acid (EACA) needed to completely inhibit fibrinolysis in canine and human plasma after induction of hyperfibrinolysis.

SAMPLES

Pooled citrated plasma from 7 dogs and commercial pooled citrated human plasma.

PROCEDURES

Concentrations of EACA from 0 μg/mL to 500 μg/mL and of TEA from 0 μg/mL to 160 μg/mL were added to pooled citrated canine and human plasma. Hyperfibrinolysis was induced with 1,000 units of tissue plasminogen activator/mL, and kaolin-activated thromboelastography was performed in duplicate. The minimum concentrations required to completely inhibit fibrinolysis 30 minutes after maximum amplitude of the thromboelastography tracing occurred were determined.

RESULTS

Minimum plasma concentrations necessary for complete inhibition of fibrinolysis by EACA and TEA in pooled canine plasma were estimated as 511.7 μg/mL (95% confidence interval [CI], 433.2 to 590.3 μg/mL) and 144.7 μg/mL (95% CI, 125.2 to 164.2 μg/mL), respectively. Concentrations of EACA and TEA necessary for complete inhibition of fibrinolysis in pooled human plasma were estimated as 122.0 μg/mL (95% CI, 106.2 to 137.8 μg/mL) and 14.7 μg/mL (95% CI, 13.7 to 15.6 μg/mL), respectively.

CONCLUSIONS AND CLINICAL RELEVANCE

Results supported the concept that dogs are hyperfibrinolytic, compared with humans. Higher doses of EACA and TEA may be required to fully inhibit fibrinolysis in dogs.

Monitoring hypercoagulability and hypofibrinolysis following acute venous Thromboembolism in children: application of the CloFAL assay in a prospective inception cohort study

Although individual thrombophilia tests are frequently performed in children with venous thromboembolism (VTE), global assays provide the opportunity to fill the gap in knowledge regarding their net impact on overall coagulative (and in some cases fibrinolytic) function. We first evaluated analytic sensitivity of the Clot Formation and Lysis (CloFAL) global assay to hypercoagulability and alterations in fibrinolysis, and then characterized changes in plasma coagulative and fibrinolytic capacities over time in children with acute VTE. In plasma ex vivo and in vitro experiments, the CloFAL assay area-under-the-curve (AUC) was analytically sensitive to hypercoagulable states, and its modified fibrinolytic index (FI2) was sensitive to both hyper- and hypofibrinolytic conditions. Clinical data and plasma samples for assay were collected during follow-up of 50 children enrolled in a prospective inception cohort study of VTE from May 2006 to June 2010. Follow-up periods were designated as follows: acute (<1 month post-event), sub-acute (1-3 months), early chronic (3-12 months), and late chronic (>12 months). Since most children were sampled at fewer than three pre-defined follow-up periods, study population findings were grouped by timepoint. AUC was significantly increased, and FI(2) significantly decreased, in the acute period of VTE when compared to healthy controls, indicating hypercoagulability and hypofibrinolysis, respectively. One-third of patients were hypercoagulable, and 23% were hypofibrinolytic, in the late chronic phase. AUC and FI(2) were strongly correlated with functional fibrinogen levels. These findings indicate the utility of the CloFAL assay in monitoring plasma coagulative and fibrinolytic capacities in children with VTE. Studies of its potential role in outcome prediction are ongoing.