Hemostasis Testing Modalities

Vocabulary practice flashcards covering veterinary diagnostic hemostasis testing, pre-analytic considerations, coagulation factor pathways, viscoelastic testing parameters, fibrinolysis assays, and endogenous anticoagulants based on Dr. Amir Kol's lecture notes.

Syringe Citrate Anticoagulation Ratio

The required ratio of sodium citrate anticoagulant to blood ($1:9$) when drawing samples with a syringe for plasma-based coagulation testing.

Intrinsic Coagulation Pathway

The contact-activated branch of secondary hemostasis comprising coagulation factors $12$, $11$, $9$, and $8$, clinically assessed by ACT and aPTT.

Extrinsic Coagulation Pathway

The coagulation cascade pathway initiated by tissue factor (TF) complexing with factor $7$, clinically evaluated by Prothrombin Time (PT).

Common Coagulation Pathway

The converging segment of the coagulation cascade where the intrinsic and extrinsic pathways unite, comprising factors $10$, $5$, $2$ (prothrombin), and $1$ (fibrinogen).

Activated Coagulation Time (ACT)

A point-of-care test performed on un-anticoagulated whole blood in specialized activator tubes incubated at $37^\circ\text{C}$, measuring the time to visual clot formation ($55\text{--}80\,\text{sec}$ in dogs, $55\text{--}85\,\text{sec}$ in cats).

ACT Factor Sensitivity Threshold

The detection limit of the Activated Coagulation Time assay; it is an insensitive test that only becomes prolonged when a single intrinsic or common pathway factor drops below $<10\%$ of normal activity.

Activated Partial Thromboplastin Time (aPTT / PTT)

A coagulation assay performed on citrated plasma with added procoagulant phospholipids, calcium, and contact activators (kaolin, silicates) that detects intrinsic and common pathway factor deficiencies ($<30\%$ activity of a single factor) and is unaffected by thrombocytopenia.

Prothrombin Time (PT)

A coagulation assay performed on citrated plasma with added phospholipids, calcium, and tissue factor reagent that detects extrinsic and common pathway deficiencies; it is unaffected by thrombocytopenia and contains a heparin inactivator.

International Normalized Ratio (INR)

A unitless mathematical ratio used to standardize Prothrombin Time (PT) results across different laboratories and reagents, calculated as $\text{INR} = \frac{\text{Patient PT}}{\text{Reference PT}}$.

PIVKA (Proteins Induced by Vitamin K Antagonism or Absence)

Inactive, non-carboxylated precursor forms of coagulation factors $2$, $7$, $9$, and $10$ that accumulate when Vitamin K is absent or antagonized.

Veterinary PIVKA Test (Thrombotest PT)

A modified PT assay with factor $5$ and fibrinogen added to the reagent that detects decreased functional activities of factors $2$, $7$, and $10$, although it is not specific for PIVKA.

Thrombin Clotting Time (TT / TCT)

An assay performed on citrated plasma where exogenous thrombin is added to cleave fibrinogen into fibrin, measuring functional fibrinogen concentration and detecting dysfibrinogenemia or fibrin polymerization inhibitors.

Clauss Fibrinogen Assay (TTclauss)

A modified thrombin time assay commonly utilized by diagnostic laboratories to quantitatively measure functional plasma fibrinogen concentration.

Russell Viper Venom Test (RVVT)

A coagulation assay using venom from Daboia species to directly activate factors $10$ and $5$ in the presence of added phospholipids, primarily used to detect anti-phospholipid antibodies (lupus anticoagulant).

Viscoelastic Testing

A methodology providing kinetic recording of global hemostasis in whole blood (or plasma/PRP) without endothelial cells, assessing clot formation, platelet-fibrin interactions, and clot lysis via platforms such as TEG, ROTEM, and Sonoclot.

Reaction Time (R) / Clot Time (CT)

The viscoelastic testing parameter (TEG $R$, ROTEM $CT$, in minutes) defining the time until the initial onset of fibrin polymerization; shortened times reflect hypercoagulability, while prolonged times reflect hypocoagulability.

K and Alpha (α) Angle

Viscoelastic kinetics parameters in TEG (analogous to ROTEM Clot Formation Time, $CFT$) reflecting the rate of fibrin polymerization; a shortened $K$ and increased $\alpha$ angle indicate hypercoagulability.

Maximum Amplitude (MA) / Maximum Clot Firmness (MCF)

Viscoelastic parameters (TEG $MA$ in $\text{mm}$ and $G$ in $\text{dyn/sec}^2$; ROTEM $MCF$ in $\text{mm}$) measuring maximal clot strength dependent on platelet count, platelet function, and fibrinogen.

LY30 and LY60

Viscoelastic parameters measuring percentage clot lysis $30$ and $60\,\text{minutes}$ after maximal clot strength (analogous to ROTEM $CLI30$ and $CLI60$), where elevated values indicate hyperfibrinolysis.

Fibrin/ogen Degradation Products (FDPs)

Breakdown products resulting from plasmin cleavage of fibrinogen and soluble fibrin, measured in $\mu\text{g/ml}$ by latex agglutination immunoassays; increased with hyperfibrinolysis, hyperfibrinogenolysis, or decreased hepatic clearance.

D-dimers

Specific neoantigen cleavage fragments generated exclusively by plasmin degradation of factor $13\text{a}$-cross-linked fibrin, measured in $\text{ng/ml}$ via latex agglutination immunoassays.

Tissue Plasminogen Activator (tPA)

An endothelial enzyme that converts plasminogen to active plasmin to trigger fibrinolysis; it is physiologically inhibited by plasminogen activator inhibitors (PAIs).

Thrombin-Activatable Fibrinolysis Inhibitor (TAFI)

An enzyme activated by thrombin that suppresses fibrinolysis by directly inhibiting plasmin-mediated breakdown of fibrin clots.

Alpha-2-Antiplasmin (α2-antiplasmin)

A primary circulating endogenous inhibitor (along with $\alpha_2$-macroglobulin) that rapidly inactivates free plasmin in plasma.

Antithrombin (AT / ATIII)

An endogenous anticoagulant serine protease inhibitor measured by functional chromogenic assays; only decreased activity is clinically significant (resulting from decreased hepatic production, protein-losing nephropathy/enteropathy, or consumptive coagulopathies).

Protein C

An endogenous anticoagulant protein evaluated via chromogenic assays; decreased levels occur from liver dysfunction, congenital deficiency, or Vitamin K antagonism, while increased activation is seen in Trauma-Induced Coagulopathy.