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The Diagnostic Pitfall: DOACs and Activated Partial Thromboplastin Time
Mohamed Hanafy Morsy/LInkedIn
Nov 28, 2025, 16:44

The Diagnostic Pitfall: DOACs and Activated Partial Thromboplastin Time

Mohamed Hanafy Morsy, Associate Professor of Clinical Pathology, Hematopathologist at Makkah Health Cluster, posted on LinkedIn:

”Lab staff + Cardiology Colleagues – Quick 30-second read that will save you confusion forever

The Diagnostic Pitfall: Direct Oral Anticoagulants (DOACs) and Activated Partial Thromboplastin Time (aPTT)

Scenario: A patient is receiving therapeutic anticoagulation with a direct Factor Xa inhibitor (e.g., Apixaban, Rivaroxaban). Routine or emergent coagulation screening returns an aPTT result that is unmeasurably short, <25 seconds, or within the institutional reference interval.

Your reaction?

A) Panic – “The patient has NO anticoagulation”

B) Call the lab – “Your machine is broken”

C) Relax – This is 100 % normal and expected

The correct answer is C

Apixaban (and all DOACs) have minimal to no effect on aPTT.
A super-low aPTT does NOT mean the drug isn’t working.
Ideal lab comment to add automatically when apixaban is on the chart:

“The aPTT result is not validated for assessing the efficacy of Direct Factor Xa Inhibitors. If quantitative assessment of drug concentration is required, order the drug-specific Chromogenic Anti-Xa Assay.”

Let’s stop the 2 a.m. pages to hematology for this.”

Apixaban

 

Keep up with Hemostasis Today.

Activated Partial Thromboplastin Time Anticoagulation Apixaban aPTT coagulation Direct Oral Anticoagulants DOAC Factor Xa inhibitor Health Hematology Hemostasis Hemostasis Today Lab Medicine Lab Tests Medicine thrombosis
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