Lab eval of 2nd Hemostasis

What is secondary hemostasis?

Formation of a stable fibrin clot through the coagulation cascade.

What are the factors of the intrinsic pathway?

Factors XII, XI, IX, and VIII.

What are the components of the extrinsic pathway?

Factor VII and tissue factor (TF).

What are the factors of the common pathway?

Factors X, V, II, I, and XIII.

What does clotting time measure?

Time required for blood to form a visible fibrin clot.

Which pathways are primarily evaluated by clotting time?

Intrinsic and common pathways.

What is the coagulation test?

A test measuring the composite action of plasma coagulation factors.

What are the two micro methods for clotting time?

Slide or drop method; capillary tube method.

What is the principle of the capillary tube method?

Blood clots in a narrow glass capillary through contact activation.

What is the normal capillary tube clotting time?

3–6 minutes.

What is another name for the capillary tube method?

Dale and Laidlaw's method.

What is the principle of the Lee-White method?

Measures time for freshly collected blood to form a firm clot in glass tubes at 37°C.

What does the Lee-White method evaluate?

Integrity of the intrinsic coagulation system.

What is the normal Lee-White clotting time?

5–10 minutes.

What is one advantage of the Lee-White method?

It is a more accurate, standardized method that can be run with a control.

What can shorten Lee-White clotting time?

Vigorous agitation of the tubes.

What conditions may prolong whole blood clotting time?

Hemophilia A or B, severe liver disease, DIC, anticoagulants, and fibrinogen abnormalities.

What is activated coagulation time (ACT)?

Time for fresh blood to clot at 37°C with surface-contact activation.

What does ACT evaluate?

Overall activity of the intrinsic clotting system.

What is the normal ACT in the lecture?

1–2 minutes.

What factors affect ACT results?

Heparin, platelet count/function, hypothermia, IV-fluid dilution, factor deficiencies, and medications.

What is plasma recalcification time (PRT)?

A test measuring the intrinsic coagulation mechanism after recalcification.

How does PRT compare with whole blood clotting time?

It is more sensitive and may detect abnormalities missed by whole blood clotting time.

What is the normal PRT?

90–250 seconds.

What is activated recalcification time (ART)?

A test using platelet-rich plasma, calcium chloride, and a contact activator.

What is the normal ART?

Less than 50 seconds.

What is the function of platelet-rich plasma in ART?

Provides coagulation factors and a PF3 surface.

What is the function of calcium chloride in ART?

Replaces calcium removed by citrate and initiates clotting.

What is the function of Cellite in ART?

Acts as a contact activator of the intrinsic pathway.

What may prolonged ART indicate?

Intrinsic factor deficiencies, severe liver disease, low fibrinogen, anticoagulants, or platelet functional defects.

What pathways does PTT evaluate?

Intrinsic and common pathways.

What is APTT primarily used to detect?

Deficiencies of intrinsic factors VIII, IX, XI, and XII.

What is the normal APTT in the lecture?

25–35 seconds.

What is DAPTT used for?

Differentiating factor deficiencies from circulating anticoagulants.

What is DPTT?

A modified PTT using patient plasma and correcting factor reagents.

Which factor reagent corrects the PTT in hemophilia A?

Factor VIII reagent.

Which factor reagent corrects the PTT in hemophilia B?

Factor IX reagent.

What pathways does prothrombin time (PT) evaluate?

Extrinsic and common pathways.

Which factors may be detected as deficient by PT?

Factors I, II, V, VII, and X.

What is the Quick one-stage PT method?

A method using tissue thromboplastin and calcium added to plasma to measure clot formation.

What is the Owren and Aas method?

A two-stage test estimating prothrombin and proconvertin levels.

What are advantages of the Owren and Aas method?

More sensitive than the Stanley Brown method, permits mailed samples, and is not affected by heparin.

What is Owren's Thrombotest used for?

Monitoring coumarin anticoagulant therapy; the lecture describes it as highly sensitive.

What is a fibrometer?

An electromechanical semiautomated instrument used to detect clot formation.

How does a fibrometer detect clotting?

By sensing changes in electrical conductivity or mechanical resistance.

What is the Stypven time?

Russell's viper venom time; distinguishes factor X from factor VII deficiencies.

Which factor deficiency is not detected by Stypven time according to the lecture?

Factor VII deficiency.

What is prothrombin activity or index?

A percentage expressing prothrombin activity relative to the control PT.

What is the formula for PT activity in the lecture?

PT activity (%) = control PT in seconds ÷ patient PT in seconds × 100.

What is the International Normalized Ratio (INR) used for?

Standardized reporting of PT, especially for oral anticoagulant monitoring.

What is the INR formula shown in the lecture?

Patient PT ÷ mean normal PT.

What is the International Sensitivity Index (ISI)?

A standard describing the sensitivity of a PT thromboplastin reagent.

What does an ISI greater than 1.0 indicate in the lecture?

Lower sensitivity.

What does an ISI less than 1.0 indicate in the lecture?

Higher sensitivity.

What does the prothrombin consumption test (PCT) assess?

Platelet phospholipid activity.

What can a short PCT with normal PT and PTT indicate?

PF3 deficiency associated with thrombocytopenia or thrombopathia.

What does the thromboplastin generation test evaluate?

The entire intrinsic pathway and the capacity to generate thromboplastin.

What are two thromboplastin generation test methods?

Biggs and Macfarlane method; Hick's-Pitney kaolin modification.

What does thrombin time (TT) measure?

Availability of functional fibrinogen and time for clot formation after thrombin addition.

What is the principle of thrombin time?

Add thrombin reagent to citrated plasma and measure clotting time.

What is the normal thrombin time in the lecture?

10–20 seconds.

What is thrombin time sensitive to?

Heparin inhibition.

What is the Fibrindex test?

A commercial test in which thrombin produces a clot in plasma containing fibrinogen.

What are the Fibrindex normal values in the lecture?

Plasma: 5–10 seconds; firm clot without serum: 30–60 seconds.

What is the FIT-test?

An immunological slide test detecting fibrinogen through agglutination of fibrinogen-coated RBCs by latex anti-human fibrinogen reagent.

What does agglutination indicate in the FIT-test?

Presence of fibrinogen.

What is the fibrinogen titer method?

Serially dilutes plasma with thrombin; the highest dilution showing a fibrin clot is the titer.

How is plasma fibrinogen quantified?

By gravimetric, nephelometric, chemical, immunologic, or precipitation methods.

Name methods of plasma fibrinogen assay listed in the lecture.

Ellis and Stransky; Stirland's; Partfantjevet et al. turbidimetric; Ratnoff and Menzie; fibrin clot method.