Hemostasis Testing: Specimen Collection

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Questions and Answers

What is the primary concern during specimen collection for hemostasis testing?

Maintaining a consistent temperature of 37°C during collection.
Ensuring the sample is collected in a glass container.
Preventing premature activation of the clotting process. (correct)
Vigorous mixing of the sample immediately after collection.

Contamination with tissue thromboplastin primarily affects which coagulation pathway?

Common pathway
Intrinsic pathway
Fibrinolytic pathway
Extrinsic pathway (correct)

Why are glass containers generally avoided in hemostasis testing?

Glass interferes with platelet aggregation.
Glass causes factor degradation.
Glass is difficult to sterilize properly.
Glass activates the intrinsic pathway and attracts platelets due to its negatively charged surface. (correct)

Which of the following factors are labile at room temperature, requiring careful temperature control during specimen handling?

Factors V and VIII (B) Signup and view all the answers

Prolonged tourniquet application during blood collection can lead to which of the following?

Increased concentration of von Willebrand factor and factor VIII. (D) Signup and view all the answers

Which needle gauge is generally recommended for hemostasis sample collection to avoid hemolysis?

20-gauge needle (A) Signup and view all the answers

What is the purpose of using silicone-coated syringes or evacuated tubes in hemostasis sample collection?

To minimize platelet activation and clotting (D) Signup and view all the answers

Which anticoagulant is considered the most satisfactory for platelet aggregation studies?

Trisodium citrate (D) Signup and view all the answers

What is the ideal ratio of blood to anticoagulant when using trisodium citrate for coagulation testing?

9:1 (D) Signup and view all the answers

Why does a specimen with a high hematocrit require special consideration when using trisodium citrate?

It has excess unbound citrate, which can prolong coagulation tests. (B) Signup and view all the answers

Which anticoagulant is unsuitable for routine coagulation testing due to its interference with the fibrinogen-thrombin reaction?

EDTA (B) Signup and view all the answers

How does heparin exert its anticoagulant effect?

By acting with antithrombin III to inhibit coagulation stages (B) Signup and view all the answers

Changes in pH can affect coagulation tests by:

Prolonging clotting times. (D) Signup and view all the answers

At what temperature are Factors VII and XI prematurely activated?

4°C (C) Signup and view all the answers

What centrifugation conditions are typically used to obtain platelet-poor plasma (PPP) for coagulation testing?

2000 g for 10 minutes (A) Signup and view all the answers

Which portion of the plasma layer should be used for testing after centrifugation?

Only the upper ¾ of the plasma layer (B) Signup and view all the answers

The Lee and White whole blood coagulation time test primarily measures the function of which coagulation pathways?

Intrinsic and common pathways (D) Signup and view all the answers

What is a key limitation of the Lee and White whole blood coagulation time test?

Insensitivity to factor deficiencies (C) Signup and view all the answers

In the Plasma Recalcification Time test, what components are present in PRP (platelet-rich plasma) that are necessary for creating a fibrin clot, except for what?

Calcium (B) Signup and view all the answers

Which of the following best describes the utility of the activated partial thromboplastin time (APTT) assay?

Screens for deficiencies in the intrinsic and common pathways. (A) Signup and view all the answers

What component is present in partial thromboplastin reagent?

Only the phospholipid component (A) Signup and view all the answers

What is the purpose of including activators like kaolin or ellagic acid in the APTT reagent?

To activate contact factors in the intrinsic pathway (C) Signup and view all the answers

What is the primary purpose of the APTT assay in clinical practice?

Monitoring heparin therapy. (A) Signup and view all the answers

The prothrombin time (PT) test is used to assess deficiencies in which coagulation pathway(s)?

Extrinsic and common pathways (A) Signup and view all the answers

What is the test of choice for monitoring anticoagulant therapy with Vitamin K antagonists (e.g., warfarin/coumarin)?

Prothrombin Time (PT) (B) Signup and view all the answers

What is the purpose of the International Normalized Ratio (INR) in coagulation testing?

To standardize PT reporting worldwide (D) Signup and view all the answers

In the context of INR, what does a lower International Sensitivity Index (ISI) of a thromboplastin reagent indicate?

Higher sensitivity of the reagent. (B) Signup and view all the answers

What is the principle behind the Stypven Time (Russel's viper venom time) test?

It bypasses the action of factor VIII and directly activates Factor X to Xa (A) Signup and view all the answers

The thrombin time (TT) is prolonged by which of the following conditions?

Presence of heparin or direct thrombin inhibitors (C) Signup and view all the answers

What is the key principle behind the Reptilase time test that distinguishes it from the thrombin time?

Reptilase is unaffected by heparin. (A) Signup and view all the answers

Flashcards

Primary concern in hemostasis testing

Prevent premature activation of the clotting process.

Contamination with tissue thromboplastin

Tissue factor activating the extrinsic pathway.