Lab eval of Fibrinolysis

Fibrinolysis

Enzymatic breakdown of fibrin in blood clots.

Plasmin

Key enzyme responsible for degradation of fibrin.

Alpha-2 antiplasmin

Plasma inhibitor that inactivates plasmin.

Whole blood clot lysis time

Test that evaluates clot dissolution due to plasmin activity.

Normal whole blood clot lysis time

Clot lysis occurs after 24 hours.

Excessive plasmin activity in whole blood clot lysis

Clot lysis occurs in less than 24 hours.

Deficient plasmin activity

Clot remains beyond 72 hours in whole blood clot lysis.

Diluted blood clot lysis time

Test used to screen excessive fibrinolysis and monitor activity in MI and stroke.

Principle of diluted blood clot lysis time

Plasmin inhibitors lose activity upon dilution.

Plasma clot lysis time

Test using recalcified plasma clot incubated at 37°C and observed for lysis over 48 hours.

Normal plasma clot lysis time

Clot lysis in 6–10 hours.

Prolonged plasma clot lysis time

Lysis beyond the normal interval; lecture associates this with high plasmin inhibitors.

Shortened plasma clot lysis time

Clot lysis in less than 6 hours.

Euglobulin lysis time (ECLT)

Screening procedure measuring overall fibrinolytic activity.

Euglobulin fraction

Fraction containing fibrinogen, plasminogen, and plasminogen activators, with only traces of antiplasmins.

ECLT principle

Lysis of a fibrin clot formed by adding thrombin measures fibrinolytic activity.

1% acetic acid in ECLT

Precipitates the euglobulin fraction from diluted plasma.

Shortened ECLT

Less than 2 hours; indicates excessive fibrinolysis.

Prolonged ECLT

Beyond 2 hours; indicates deficient plasminogen activator.

Fibrinogen level affecting ECLT

Below 80 mg/dL makes fibrinolytic activity difficult to measure.

Reference fibrinogen level in lecture

200–400 mg/dL.

ECLT specimen handling

Set up immediately after collection and keep plasma on ice.

Protamine sulfate turbidity test

Test detecting fibrin monomers and fibrin degradation products.

Protamine sulfate test procedure

Mix patient/control plasma with varying protamine dilutions; incubate at room temperature for 30 minutes.

Positive protamine sulfate test

Turbid; indicates presence of fibrin monomers.

Negative protamine sulfate test

Non-turbid; indicates absence of fibrin monomers.

D-dimer

Specific fragment from degradation of cross-linked fibrin.

D-dimer clinical significance

Indicates ongoing fibrin formation and breakdown.

D-dimer negative cutoff in lecture

Less than 0.5 µg/mL.

Elevated D-dimer in lecture

Greater than 0.5 µg/mL; may occur in DIC, DVT, PE, or stroke.

Very high D-dimer in lecture

Greater than 2 µg/mL; associated with severe DIC and sepsis.

Preferred D-dimer specimen

Fresh citrated plasma.

Serum D-dimer compared with plasma

Serum has lower D-dimer levels than plasma.

Enzyme immunoassay for D-dimer

Quantitative, sensitive assay that is time-consuming.

Latex bead D-dimer assay

Rapid, simple, semiquantitative method useful for point-of-care testing.

Fibrin degradation product (FDP) assay

Uses antibodies against FDP; increased FDP signifies active fibrinolysis.

Tissue plasminogen activator (tPA) antigen

Plasma concentration can be estimated by enzyme immunoassay.

Low tPA levels

Impaired fibrinolysis and association with thrombotic disorders.

Plasminogen activator inhibitor-1 (PAI-1) assay

Assesses PAI-1 antigen or activity using available methods.

Prothrombin fragment 1.2 (F1.2)

Sensitive biological marker of thrombin generation and factor Xa activity.

Plasma antithrombin

Inactivates thrombin and other serine proteases, including activated factors XII, XI, X, and IX.

Effect of heparin on antithrombin

Accelerates antithrombin-mediated inactivation of thrombin.

Plasma thrombin time

Measures functional fibrinogen availability and is sensitive to heparin inhibition.

Prolonged thrombin time

May result from low fibrinogen, abnormal fibrinogen function, DIC, or abnormal fibrinolysis.

Lupus anticoagulant

Autoantibody associated with excess clot formation despite its name.

Heparin monitoring

PTT, as stated in the lecture.

Warfarin monitoring

PT, as stated in the lecture.