Isolated Elevated APTT
OVERVIEW
- APTT measures the activity of the intrinsic and common pathways of coagulation
CAUSES
- 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)
INVESTIGATIONS
- 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
- PracticalHaemostasis.com — Activated Partial Thromboplastin Time (APTT)
Critical Care
Compendium
Chris is an Intensivist and ECMO specialist at The Alfred ICU, where he is Deputy Director (Education). He is a Clinical Adjunct Associate Professor at Monash University, the Lead for the Clinician Educator Incubator programme, and a CICM First Part Examiner.
He is an internationally recognised Clinician Educator with a passion for helping clinicians learn and for improving the clinical performance of individuals and collectives. He was one of the founders of the FOAM movement (Free Open-Access Medical education) has been recognised for his contributions to education with awards from ANZICS, ANZAHPE, and ACEM.
His one great achievement is being the father of three amazing children.
On Bluesky, he is @precordialthump.bsky.social and on the site that Elon has screwed up, he is @precordialthump.
| INTENSIVE | RAGE | Resuscitology | SMACC
