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Table 2 Indications and limitations of tests available in the hemostasis laboratory

From: Management of the thrombotic risk associated with COVID-19: guidance for the hemostasis laboratory

  Main Limitations Indications in COVID-19
Evaluation of the thrombotic risk Screening of thromboembolic events Prognosis: disease severity Diagnosis of DIC Detection of HIT Monitoring of unfractionated heparin
Platelet count Many causes of thrombocytopenia in the critically ill patient    X X X  
APTT Major influence of preanalytical step      X (*) X
Differences of APTT reagents in their sensitivity to unfractionated heparin, lupus anticoagulant and inflammatory syndrome
Prothrombin Time Influence of the preanalytical step     X   
Influence of fibrinogen level
Fibrinogen (Clauss) Lack of sensitivity for the diagnosis of DIC (mostly in infectious/inflammatory setting) X   X X   
Possibility of interference of direct thrombin inhibitors with some reagents
D-dimers Decreased analytical performances in high D-dimers values X X X X   
Production dependent on the fibrinolytic activity
Cut-offs non commutable between reagents
Soluble fibrin complexes (AKA ‘Fibrin monomers’) Preliminary validation only   X   X   
Not evaluated in COVID-19
Cut-offs non commutable between the reagents
Fibrinolysis capacity tests Fibrinolysis is assessed in non-physiological conditions X   X    
Large array of methods
Not evaluated in COVID-19
Anti-Xa activity Inter-reagent variability       X
Influence of presence/absence of exogenous AT in the reagent
Only available 24 h a day 7 days a week in a fraction centers
Viscoelastic tests Not evaluated in COVID-19 X   X    X
Lack of standardization between instruments and centers
Thrombin generation assays Not evaluated in COVID-19 X      
High sensitivity to heparins
Limited availability in clinical practice
  1. (*) Heparin resistance can be due to HIT.
  2. Note: the assessment of the in vivo effect of (any) anticoagulant treatment could be assisted with the monitoring of fibrin-related markers (D-dimers; fibrin monomers)