IVD of Coagulation
What is Blood Coagulation?
Blood coagulation involves complex interaction between cellular structures, proteins and biochemical reactions. It is a protective mechanism that is activated when blood vessels are damaged. The process is tightly controlled by the body to ensure that clotting happens exactly where it's needed and doesn't lead to an undesirable clot.
The Coagulation Process
Vascular Phase:
When a blood vessel is injured, the immediate response is vasoconstriction, a reflex that narrows the vessel to reduce blood flow and minimize blood loss.
This phase also involves the release of chemical signals that initiate the next stages of coagulation.
Platelet Phase:
A damaged blood vessel immediately causes vasoconstriction, a reflex that contracts the vessel to shut off the flow and stop blood loss. This also triggers chemical messengers that initiate the next stages of coagulation.
Coagulation Phase:
This phase involves a cascade of events known as the coagulation cascade, characterized by the activation of various clotting factors.
There are two pathways: the intrinsic and extrinsic pathways, which converge into a final common pathway leading to clot formation.
The end result is the transformation of fibrinogen, a soluble plasma protein, into fibrin threads that weave through the platelet plug, solidifying it into a stable blood clot.
Regulation and Resolution
Regulation: Coagulation is tightly regulated by anticoagulants and regulatory mechanisms ensuring it occurs only where and when needed.
Resolution: Once the vessel is healed, fibrinolysis occurs, breaking down the clot to restore normal blood flow.
How serious is coagulation disorder?
Blood coagulation, while essential, can become problematic if not controlled effectively. Inadequate coagulation can lead to excessive bleeding and conditions such as hemophilia. Conversely, excessive coagulation can cause thrombosis, where clots form inappropriately within blood vessels, potentially leading to life-threatening conditions such as strokes, heart attacks, or pulmonary embolisms.
Types of Blood Clotting Disorders
Hemophilia: A hereditary disorder characterized by the deficiency of certain clotting factors, leading to excessive bleeding.
Von Willebrand Disease: A genetic disorder caused by deficient or defective von Willebrand factor, a protein critical for platelet aggregation.
Deep Vein Thrombosis (DVT): Formation of clots in deep veins, typically in the legs, which can dislodge and lead to pulmonary embolism.
Thrombophilia: A predisposition to developing blood clots due to an abnormality in coagulation.
Disseminated Intravascular Coagulation (DIC): A serious disorder in which the proteins that control blood clotting become abnormally active.
Signs and Symptoms of Blood Clotting Disorders
Hemophilia: Prolonged bleeding, spontaneous bleeding into joints, muscle hematomas.
Von Willebrand Disease: Easy bruising, frequent nosebleeds, heavy menstrual bleeding.
DVT: Swelling and pain in the affected leg, warmth, and redness.
Pulmonary Embolism: Shortness of breath, chest pain, coughing.
DIC: Bleeding from multiple sites, bruising, blood clots, and organ failure in severe cases.
Treatment of Blood Clotting Disorders
Hemophilia: Treatment involves replacing the missing clotting factors through regular infusions, especially before surgeries or injury-prone activities.
Von Willebrand Disease: Desmopressin (DDAVP) to stimulate the release of stored von Willebrand factor, or blood products like cryoprecipitate when necessary.
DVT and Pulmonary Embolism: Anticoagulants such as heparin and warfarin are used to prevent new clots from forming. Thrombolytics may be used to dissolve existing clots.
Thrombophilia: Long-term use of anticoagulants to manage clot risk.
DIC: Focus on treating the underlying cause and managing symptoms with blood products to replace depleted clotting components.
Diagnostic Methods and biomarkers
Coagulation diagnostics, often performed in clinical laboratories, are essential for assessing the blood's ability to clot properly. These tests help diagnose bleeding disorders, monitor patients on anticoagulation therapy, and assess liver function.
Prothrombin Time (PT) and International Normalized Ratio (INR):
Markers: Measures the time it takes for blood to clot by assessing the extrinsic and common coagulation pathways. It evaluates factors I (fibrinogen), II (prothrombin), V, VII, and X.
Uses: Monitoring patients on warfarin therapy, liver function tests, diagnosing clotting disorders.
Activated Partial Thromboplastin Time (aPTT):
Markers: Evaluates the intrinsic and common pathways by measuring factors VIII, IX, XI, XII, and common pathway factors.
Uses: Monitoring heparin therapy, diagnosing bleeding disorders like hemophilia.
Thrombin Time (TT):
Markers: Measures the time it takes for a clot to form after thrombin is added to plasma. It assesses the conversion of fibrinogen to fibrin.
Uses: Evaluating disorders of fibrinogen and detecting inhibitors of thrombin.
Fibrinogen Level:
Markers: Quantifies the amount of fibrinogen, a key protein in the clotting process.
Uses: Diagnosing bleeding disorders and monitoring severe liver disease or disseminated intravascular coagulation (DIC).
D-Dimer:
Markers: Indicates fibrin degradation products in the blood.
Uses: Diagnosing thrombotic conditions like deep vein thrombosis (DVT), pulmonary embolism (PE), and DIC.
Platelet Function Tests:
Markers: Evaluates how well platelets clump together to form a platelet plug.
Uses: Diagnosing platelet function disorders and monitoring anti-platelet therapy.
Factor Assays:
Markers: Measures the specific levels of individual clotting factors.
Uses: Diagnosing specific clotting factor deficiencies or defects.
Bleeding Time:
Markers: Measures how quickly small blood vessels in the skin stop bleeding.
Uses: Rarely used today but can indicate platelet function problems.
Anti-factor Xa Test:
Markers: Measures the activity of factor Xa inhibitors.
Uses: Monitoring low molecular weight heparin or direct oral anticoagulants (DOACs).
Case study
Case 1: Manzoni F, Raffaeli G, Cortesi V, Amelio GS, Amodeo I, Gulden S, Cervellini G, Tomaselli A, Colombo M, Artoni A, Ghirardello S, Mosca F, Cavallaro G. Viscoelastic coagulation testing in Neonatal Intensive Care Units: advantages and pitfalls in clinical practice. Blood Transfus. 2023 Nov 13;21(6):538-548. doi: 10.2450/2023.0203-22. PMID: 36795342; PMCID: PMC10645350.
Conventional coagulation tests do not provide reliable information as they only explore the procoagulants during the neonatal period. In contrast, viscoelastic coagulation tests (VCTs), such as viscoelastic coagulation monitoring (VCM), thromboelastography (TEG or ClotPro), and rotational thromboelastometry (ROTEM), are point-of-care assays that provide a quick, dynamic and global view of the hemostatic process, allowing prompt and individualized therapeutic intervention when necessary.
Fig3. Representative viscoelastic coagulation trace in specific conditions (A) Comparison of thromboelastography (TEG) functional fibrinogen assay (FLEV-TEG) (green tracing) with citrated whole blood sample (black lines). (B) TEG during extracorporeal membrane oxygenation (ECMO). Effect of heparin on TEG testing during neonatal ECMO: the green lines represent kaolin activation without heparinase; the black lines indicate kaolin activation with heparinase. (C) TEG reading of thrombocytopenia in a preterm newborn (31 weeks of gestational age) on the 47th day of life. The blood count showed thrombocytopenia (24×109/L platelets). (D) Viscoelastic coagulation monitoring of thrombocytopenia in a preterm newborn (31 weeks of gestational age) on the first day of life. The blood count showed thrombocytopenia (platelets 44×109/L). A10: clot amplitude at 10 minutes; A20: clot amplitude at 20 minutes; CFT: clot formation time; CI: coagulation index; CI: coagulation index; CT: clotting time; FLEV: functional fibrinogen level; K: kinetics time; LI45: lysis index at 45 minutes; LY30 or LI30: lysis index at 30 minutes; MA: maximum amplitude; MCF: maximum clot firmness; R: reaction time.Case 2: Klompas AM, van Helmond N, Juskewitch JE, Pruthi RK, Sexton MA, Soto JCD, Klassen SA, Senese KA, van Buskirk CM, Winters JL, Stubbs JR, Hammel SA, Joyner MJ, Senefeld JW. Coagulation profile of human COVID-19 convalescent plasma. Sci Rep. 2022 Jan 12;12(1):637. doi: 10.1038/s41598-021-04670-1. PMID: 35022488; PMCID: PMC8755772.
Convalescent plasma is used to treat COVID-19. The aim of this study was to evaluate the coagulation profile of COVID-19 convalescent plasma. Clotting times and coagulation factor assays were compared between fresh frozen plasma, COVID-19 convalescent plasma, and pathogen-reduced COVID-19 convalescent plasma.
Fig4. Coagulation profile of COVID-19 convalescent plasma (purple), pathogen reduced COVID-19 convalescent plasma (green), and standard fresh frozen plasma (yellow). The following measurements were made: prothrombin time (PT, s), activated partial thromboplastin time (aPTT, s), thrombin time (TT, s), fibrinogen (FGN, mg/dL), D-Dimer (D-D, ng/dL fibrinogen equivalent units [FEU]), von Willebrand factor (vWF) activity (%), von Willebrand factor antigen (%), various coagulation factors II, V, VII–XII (FII, FV, FVII–FXII, %), protein S (PS) activity (%), protein C (PC) antigen (%), and alpha-2 plasmin inhibitor (a2-PI, %). Individual data are represented as symbols and summary statistics (mean ± standard deviation [SD]) are represented as bar charts. Grouped data are compared using one-way analysis of variance with Tukey's honestly significant difference (HSD) post hoc test to determine p values; *p < 0.05; **p < 0.01; and ***p < 0.001). Horizontal bars above given columns indicate the comparisons being made. Whole blood reference ranges are denoted by grey filled areas bound by dotted black lines. Reference ranges are not available for FGN, FV:C, FVIII:C, and PC antigen.