Evaluation of International Council for Standardization in Haematology Recommendations on Activated Partial Thromboplastin Time Mixing Tests Using an Automated Haemostasis Analyser

When using lupus-insensitive reagents, APTT-mixing tests are of limited value in discriminating between factor deficiencies, lupus anticoagulants, or inhibitors. Incubated mixing tests are essential when diagnosing a FVIII-inhibitor. Rather than perform mixing tests, it is better to be guided by clinical presentation and perform further investigations as appropriate, including analysis of anti-Xa activity for the presence of a direct factor-Xa inhibiting anticoagulant, factor assays in patients with bleeding (or with suspected acquired haemophilia A), and lupus anticoagulant assays in patients with no bleeding.