Isolated prolonged aPTT
BioMG follows French guidelines. Adapt it to the guidelines and the tests available where you practise.
Recent bleeding with prolonged aPTT: emergency (acquired haemophilia)
- Haematology opinion or haemophilia treatment centre the same day.
- Avoid any invasive procedure before the opinion (prevent iatrogenic bleeding).
Incidentally found prolonged aPTT, without bleeding
Laboratory tests (well-filled citrate tube, see the note)
- State on the prescription: “isolated prolonged aPTT, to be investigated” and any anticoagulant treatment.
- PT, aPTT (repeat, off anticoagulant treatment)
- aPTT mixing test with control plasma (screening for a circulating anticoagulant)
- Factors VIII, IX and XI
- Screen for von Willebrand disease (von Willebrand factor activity, factor VIII)if neededAbnormal personal bleeding history or unexplained prolonged aPTT: these are the usual reasons for investigating von Willebrand disease [6]. Von Willebrand factor is interpreted according to ABO group [3].
- State the ABO blood group on the prescription if known (blood group card).
- ABO blood group (only if not known, to interpret von Willebrand factor)if neededTesting for von Willebrand disease in a patient whose blood group is unknown: von Willebrand factor is interpreted according to ABO group [3], its levels being 25 to 35% lower in group O subjects [7]. Do not request it routinely: the diagnostic thresholds apply whatever the group [6].
- Lupus anticoagulant (at least two tests including dRVVT)if neededThrombosis or autoimmune disease: the French laboratory fee schedule (NABM) reserves the procedure for acquired thrombophilia or autoimmune disease, context specified by the prescriber [3].
Do not order
Before an invasive procedure or surgery
- No routine haemostasis tests: personal and family bleeding history, examination.
Only if the history, examination or treatment justify it
- PT, aPTTif neededLiver disease, malabsorption or undernutrition, haematological disease, anticoagulant treatment, adult who cannot be questioned, or unfractionated heparin planned after the procedure [1].
- FBC (platelets)if neededSame situations as PT and aPTT, or heparin planned after the procedure (baseline count) [1].
Do not order
- PT, aPTT, platelets as routine before a procedure, with no suggestive history or examination finding: not recommended, whatever the age (except a child who is not yet walking), the procedure and the anaesthesia [1].
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