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Prothrombin time and international normalised ratio: Diagnostic tests

CPD Hours



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Medical and surgical nursing


The content of this module is relevant to nurses and midwives providing care in a variety of healthcare settings. It defines what the prothrombin time (PT) and international normalised ratio (INR) blood tests are and how they help to determine a patient’s coagulation status and risk of bleeding.

This module also discusses coagulation processes, indications for PT/INR testing, blood specimen collection and testing procedures, interpretation of results, and limitations of PT/INR testing.

Learning Objective

At the end of this module participants will be able to:

  • Define prothrombin time (PT) and international normalised ratio (INR).
  • Provide a brief explanation of coagulation processes.
  • Discuss indications for PT/INR testing.
  • Describe important procedural points for blood specimen collection and testing.
  • Explain the interpretation of test results, including normal and abnormal ranges.
  • Discuss the limitations of PT/INR testing.

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