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Questions and Answers
What is the normal range for prothrombin time (PT)?
What is the normal range for prothrombin time (PT)?
A platelet count higher than 450,000/μL indicates thrombocytopenia.
A platelet count higher than 450,000/μL indicates thrombocytopenia.
False
What is the normal range for the International Normalized Ratio (INR)?
What is the normal range for the International Normalized Ratio (INR)?
0.8–1.1
Thrombocytopenia can be caused by __________.
Thrombocytopenia can be caused by __________.
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Match the following conditions with their corresponding causes of thrombocytosis:
Match the following conditions with their corresponding causes of thrombocytosis:
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What is the increased PT associated with?
What is the increased PT associated with?
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Activated Partial Thromboplastin Time (aPTT) is normally between 60–70 seconds.
Activated Partial Thromboplastin Time (aPTT) is normally between 60–70 seconds.
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What does an INR of 2.5–3.5 indicate?
What does an INR of 2.5–3.5 indicate?
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Study Notes
Platelet Count
- Normal range: 150,000–450,000/μL
- Thrombocythemia (abnormal platelet count) can have various causes. These include:
- Splenectomy
- Rheumatoid arthritis
- Polycythemia vera
- Decreased platelet levels (thrombocytopenia) can be caused by:
- Hypersplenism
- Hemorrhage
- Leukemia
- DIC (Disseminated Intravascular Coagulation)
Prothrombin Time (PT)
- Normal range: 10–14 seconds
- Used to assess the extrinsic and common pathways of the clotting mechanism
- More sensitive to deficiencies in Vitamin K-dependent liver factors (II, VII, IX, and X)
- Increased levels (prolonged PT) suggest:
- Liver disease
- Vitamin K deficiency
- Disseminated intravascular coagulation (DIC)
- Hereditary factor deficiency
International Normalized Ratio (INR)
- Normal range: 0.8–1.1
- Standardizes PT results, as different thromboplastin sources can produce varying results.
- Calculated using the equation: INR = (patient PT/mean normal PT)ISI
- The ISI (International Sensitivity Index) reflects the sensitivity of the thromboplastin reagent compared to the World Health Organization standard.
- INR of 2.5–3.5 is considered normal during warfarin therapy
Activated Partial Thromboplastin Time (aPTT)
- Normal range: 30–40 seconds (PTT: 60–70 seconds)
- Used to identify deficiencies or inhibitors in the intrinsic pathway (factors VIII, IX, XI, and XII), and the final common pathway (factors II, V, and X).
- Patients on anticoagulant therapy have an aPTT of 1.5-2.5 times the control value in seconds.
- Increased levels indicate:
- Congenital clotting factor deficiencies (like von Willebrand disease or hemophilia)
- Cirrhosis of the liver
- Vitamin K deficiency
- Heparin administration
D-Dimer
- Normal range: <0.5 mcg/mL (<3 nmol/L)
- Patients on anticoagulants have a D-dimer level of 1.5 -2.5 x control value in seconds
- Marker of thrombotic activity; a fibrin degradation fragment produced during the lysis of cross-linked fibrin.
- Increased levels suggest:
- Disseminated intravascular coagulation (DIC)
- Deep Vein Thrombosis (DVT)
- Pulmonary Embolism (PE)
- Arterial thromboembolism
- During thrombolytic or defibrinating therapy
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Description
Test your knowledge on platelet counts, prothrombin time, and the International Normalized Ratio (INR) in blood coagulation. This quiz covers the normal ranges, causes for abnormalities, and implications of various conditions affecting these metrics. Assess your understanding of hematology concepts related to clotting mechanisms.
