Isolated Elevated APTT


  • APTT measures the activity of the intrinsic and common pathways of coagulation


  • Lupus anti-coagulant (antiphospholipid syndrome)
  • Heparin exposure
  • Haemophilia A and B (Factor VIII and IX deficiency respectively)
  • Factor XII deficiency
  • Factor XI deficiency
  • Contact factor deficiency e.g. prekallikrein (not clinically important)
  • Artefact (incorrect amount of blood in the tube)


  • Repeat test (to exclude artefact)
  • Coag screen and fibrinogen (if normal then excludes DIC)
  • Heparinase assay or antibodies
  • Mixing test with normal plasma (excludes clotting factor deficiency)
  • Factor assay (excludes clotting factor deficiency)
  • anticardiolipin antibody (antiphospholipid syndrome)
  • Thrombin time and reptilase time (used to establish whether heparin contamination occurred: reptilase not prolonged in heparin contamination but thrombin time is)
  • Lupus anticoagulant tests (antiphospholipid syndrome) -> APTT, dilute Russell viper venom time, kaolin clotting time, dilute PT, Textarin time, Taipan time

References and Links

CCC 700 6

Critical Care


Chris is an Intensivist and ECMO specialist at the Alfred ICU in Melbourne. He is also a Clinical Adjunct Associate Professor at Monash University. He is a co-founder of the Australia and New Zealand Clinician Educator Network (ANZCEN) and is the Lead for the ANZCEN Clinician Educator Incubator programme. He is on the Board of Directors for the Intensive Care Foundation and is a First Part Examiner for the College of Intensive Care Medicine. He is an internationally recognised Clinician Educator with a passion for helping clinicians learn and for improving the clinical performance of individuals and collectives.

After finishing his medical degree at the University of Auckland, he continued post-graduate training in New Zealand as well as Australia’s Northern Territory, Perth and Melbourne. He has completed fellowship training in both intensive care medicine and emergency medicine, as well as post-graduate training in biochemistry, clinical toxicology, clinical epidemiology, and health professional education.

He is actively involved in in using translational simulation to improve patient care and the design of processes and systems at Alfred Health. He coordinates the Alfred ICU’s education and simulation programmes and runs the unit’s education website, INTENSIVE.  He created the ‘Critically Ill Airway’ course and teaches on numerous courses around the world. He is one of the founders of the FOAM movement (Free Open-Access Medical education) and is co-creator of litfl.com, the RAGE podcast, the Resuscitology course, and the SMACC conference.

His one great achievement is being the father of three amazing children.

On Twitter, he is @precordialthump.

| INTENSIVE | RAGE | Resuscitology | SMACC

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