Normal prothrombin time is?

Appeared in: CGHS SSC - 2018

Explanation

Prothrombin Time (PT) measures the integrity of the extrinsic and common coagulation pathways.
The standard normal range for PT in a healthy adult is approximately 11 to 15 seconds, though some labs may cite a slightly narrower range like 11-13 seconds.
This test is crucial for monitoring the effectiveness of oral anticoagulant therapy, particularly with warfarin (Coumadin).
Results are often reported as an International Normalized Ratio (INR) to standardize readings between different laboratories.

Option A: This range represents the normal value for Activated Partial Thromboplastin Time (aPTT), not Prothrombin Time (PT).
Option B: A PT of 100 seconds is a critically prolonged value, indicating a very high risk of spontaneous bleeding. It is far outside any normal or therapeutic range.
Option C: This range is typical for a therapeutic aPTT level in a patient receiving intravenous heparin therapy, not a normal PT.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Normal laboratory value for Prothrombin Time (PT) as background academic context rather than a clinical decision trigger.
Nurses must know normal PT/INR and aPTT values to safely administer anticoagulants like warfarin and heparin and to monitor for bleeding or clotting complications.
A prolonged PT/INR requires holding the anticoagulant, notifying the physician, and implementing bleeding precautions (e.g., soft toothbrush, electric razor, fall prevention).
The antidote for warfarin toxicity (high INR) is Vitamin K (phytonadione), while the antidote for heparin is protamine sulfate.

How to Approach the Question

This is a factual recall question asking for a specific normal laboratory value.
First, identify the specific lab test in question: Prothrombin Time (PT).
Recall the normal range for PT from your studies. It's a fundamental value to memorize for pharmacology and medical-surgical nursing.
Compare your recalled value to the given options. The typical range is around 11-15 seconds.
Mentally differentiate PT from aPTT. aPTT has a longer normal time (around 25-40 seconds), which helps eliminate distractors that fall into that range.

Concept Tested & Keywords

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E6 Pharmacology Nursing Lilley 11e Part 2 p. 125-127

E6 Pathology-Vandana Puri & Kavita Gaur Textbook of Pathology and Genetics p. 403-405

E6 Textbook of Biochemistry for medical StudentsDM Vasudevan Part 2 — Subpart A (pp 1-239 of 478) p. 66-68

Practise the full CGHS SSC - 2018

Attempt every question from this paper in a timed mock, then review the full solution for each one.