*2.1.1 Lupus anticoagulant*

LA are heterogenous antibodies detected with a functional test that measures the ability of aPL to prolong phospholipid-dependent clotting reactions. Anti-β2GPI [15] and anti-prothombin (aPT) antibodies [16] have been identified as the main mediators of this reaction. LA detection is very challenging, as it has many pitfalls leading to either false positive or false negative results. The International Society for Thrombosis and Hemostasis (ISTH) guidelines released in 2009, updated in 2018 provided a step toward standardization of LA [17, 18]. Following those guidelines LA detection is based on the simultaneously use of two assays with different principles following a multi-step procedure, with screening, mixing and confirmation steps. The most commonly used are activated partial thromboplastin time followed by the diluted Russell's viper venom test. The presence of LA should always be confirmed by performing the assays in the presence of excess of phospholipids, with a correction of the prolongation of the times as a result.
