How to break down ANY coag question (step by step) 🩸

🚀

Greetings Gang 😈😜

PT. aPTT. TT. Reptilase. Mixing study. DRVVT.

Coag questions throw 6 tests at you and expect you to stay calm. Here's the secret: they're all asking the same 5 questions, in the same order. Every time.

1. Read the story: bleeding or clotting?

Bleeding → factor deficiency, platelets, vWD or an anticoagulant.

Clotting (DVT, PE, recurrent miscarriages) → think lupus anticoagulant.

2. Which screening test is long?

PT only → Factor VII (early warfarin, vitamin K deficiency)

aPTT only → XII, XI, IX, VIII, vWD, heparin, lupus anticoagulant

BOTH → common pathway (X, V, II, I), liver disease, DIC

Both normal but bleeding → platelets, mild vWD or Factor XIII

3. Mixing study: is something missing or blocked?

Corrects → something's MISSING (factor deficiency)

Doesn't correct → something's BLOCKING (inhibitor)

Corrects, then prolongs after 1–2 hours at 37°C → Factor VIII inhibitor

4. Pair the thrombin time with the reptilase time

TT long + reptilase NORMAL → heparin (reptilase ignores heparin 🐍)

TT long + reptilase LONG → the fibrinogen itself is the problem

5. Confirm with ONE test

Heparin → anti-Xa

Direct thrombin inhibitor → ecarin clotting time

Lupus anticoagulant → DRVVT that corrects with excess phospholipid

Factor VIII inhibitor → Bethesda assay

🧐 Try it (answer in the comments):

A hospitalized patient has a prolonged aPTT. The mix does NOT correct. TT is prolonged, reptilase is normal. What's the cause, and how do you confirm it?

I attached my Ultimate Coagulation Cascade Breakdown to this post. It covers every pathway, every factor, every snake-venom test, and a self-quiz at the end.

Want to walk through coag questions live? There are still 5 sessions left in 7 Days of Study Sessions, and today's starts at 5PM EST.

👉🏽 Join here: https://www.skool.com/microscopeviews

See you there!

— Marilyn

2 comments

How to break down ANY coag question (step by step) 🩸