Coagulation laboratory tests
Abnormal PT and PTT - causes
Reviewer: Jeremy Parsons, M.D. (see Reviewers page)
Revised: 16 June 2012, last major update June 2012
Copyright: (c) 2002-2012, PathologyOutlines.com, Inc.
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
End of Coagulation > Coagulation laboratory tests > Abnormal PT and PTT - causes
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