Coagulation
Coagulation laboratory tests
Abnormal PT and PTT - causes



Topic Completed: 1 June 2012

Revised: 7 January 2019, last major update June 2012

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PubMed Search: Abnormal PT and PTT - causes


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Table of Contents
Definition / general
Cite this page: Parsons J. Abnormal PT and PTT - causes. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/coagulationabnormalPTPTT.html. Accessed October 20th, 2019.
Definition / general
  • PT normal, PTT prolonged:
    • Deficiency of intrinsic pathway factors VIII, IX, XI, XII
    • Less commonly prekallikrein or high molecular weight kininogen
    • Also prolonged delay in transporting specimen to lab (affects factors V and VIII), presence of heparin in specimen

  • PT prolonged, PTT normal:
    • Deficiency of extrinsic pathway factor VII
    • Occasionally due to deficiency of common pathway factors fibrinogen, prothrombin, factors V or X, early Vitamin K deficiency (dietary or warfarin)

  • PT and PTT prolonged:
    • Deficiency of common pathway factors fibrinogen, prothrombin, factors V or X, or multiple factor deficiencies
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