6/17/2013

Basic testing and interpretation

By Dr. Gwen Clarke

…the way coagulation works

http://www.revespcardiol.org/en/the-new-coagulation-cascade-and/articulo/13114167/

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…the way we test

http://www.recothrom.com/about-recothrom.html

What can we test (easily)

• PTT

• PT (INR)

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• count (and morphology)

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…the way we test

http://www.recothrom.com/about-recothrom.html

What do abnormal results mean?

That depends… Clinical History Medications Which tests are abnormal How abnormal are they Is this finding long standing or new

Factor deficiency, or coagulation inhibitor

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How can you follow up?

• Repeat if unexpected • Determine if prolonged due to deficiency or inhibitor… order an inhibitor screen • Don’t treat a lab abnormality (in the absence of clinical abnormality) at least until you figure out the cause…

PT/PTT inhibitor screen

• Mix patient plasma with a normal pool of plasma. • Incubate. • Repeat PT or PTT

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http://www.usmle3.com/

Peripheral

• Review platelet morphology and look at additional findings that might impact on clotting or bleeding

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Tests for VWD

• Common bleeding disorder • May contribute to prolonged PTT (or may not) • If clinical history is suspicious: • VWF, Ristocetin Cofactor and Factor VIII are diagnostic tests • Bleeding Times are not orderable, and not necessary to make this (or any other) diagnosis

Tests for Lupus anticoagulant

• Prolonged PTT • Inhibitor screen does NOT correct • Order • Lupus anticoagulant • Antiphospholipid antibodies • Assess patient for clinical features of antiphospholipid syndrome and consider consultation

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