AIIMS Bhuvneshwar NO…: Activated partial thromboplastin time (APTT) is prolonged in?

AIIMS Bhuvneshwar NO- 2018

Pathology & Genetics

Easy

Appeared in: AIIMS Bhuvneshwar NO- 2018

Explanation

The Activated Partial Thromboplastin Time (APTT) test evaluates the function of the intrinsic and common pathways of the coagulation cascade.
Hemophilia is a genetic disorder characterized by a deficiency in clotting factors that are part of the intrinsic pathway.
Specifically, Hemophilia A is a deficiency of Factor VIII, and Hemophilia B is a deficiency of Factor IX.
A deficiency in these intrinsic pathway factors impairs the blood's ability to clot, resulting in a significantly prolonged APTT.

Option A: Bone marrow depression affects the production of blood cells (pancytopenia), not the synthesis of coagulation factors, which primarily occurs in the liver. Therefore, APTT is typically normal.
Option C: Thrombocytopenia is a low platelet count. Platelets are involved in primary hemostasis (plug formation), which is assessed by bleeding time. APTT measures secondary hemostasis (the factor cascade) and is not directly affected by platelet count.
Option D: Thrombosis is the pathological formation of a blood clot. It is a condition of hypercoagulability, the opposite of a bleeding tendency that would prolong APTT.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Interpretation of Activated Partial Thromboplastin Time (APTT) in coagulation disorders as background academic context rather than a clinical decision trigger.
Nurses must understand that APTT is the primary laboratory test used to monitor the therapeutic effectiveness of unfractionated heparin infusions. A target APTT is typically 1.5 to 2.5 times the control value.
An unexpected prolonged APTT in a patient not on heparin is a critical finding. The nurse should promptly report this to the physician as it may indicate an undiagnosed bleeding disorder like hemophilia or von Willebrand disease, increasing the risk of hemorrhage.
What if? If a patient had a prolonged Prothrombin Time (PT/INR) but a normal APTT, the nurse should suspect a defect in the extrinsic pathway. This could be due to warfarin therapy, vitamin K deficiency, or liver disease, rather than hemophilia.

How to Approach the Question

First, identify the key term in the question: 'Activated partial thromboplastin time (APTT) is prolonged'.
Recall the purpose of the APTT test: it measures the effectiveness of the 'intrinsic' and 'common' pathways of blood coagulation.
Systematically evaluate each option's relationship to the intrinsic coagulation pathway.
Consider 'Hemophilia'. Recall that Hemophilia A (Factor VIII deficiency) and Hemophilia B (Factor IX deficiency) are classic disorders of the intrinsic pathway. A deficiency here will delay clotting and prolong the APTT.
Analyze the other options. 'Bone marrow depression' and 'Thrombocytopenia' relate to blood cells and platelets, not the clotting factors of the intrinsic pathway. 'Thrombosis' is excessive clotting, the opposite of what would prolong APTT.
Based on this analysis, conclude that Hemophilia is the condition that directly causes a prolonged APTT by disrupting the intrinsic pathway.

Concept Tested & Keywords

Concept Tested: Interpretation of Activated Partial Thromboplastin Time (APTT) in coagulation disorders.
Stem keywords: Activated partial thromboplastin time, APTT, prolonged
Lead-in keywords: is prolonged in
Negative lead-in flag: false

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E6 Medicine Harrison 22e Part 1 pp. 516-518, 977-979

E6 Pathology-Vandana Puri & Kavita Gaur Textbook of Pathology and Genetics p. 402-404