Mixing studies for lupus anticoagulant: does it matter how we mix?

Although clear and detailed recommendation regarding the lupus anticoagulant mixing test exist, various sources of NPP are used. We decided to inspect the possible differences in mixing studies depending on the mixing media. Four types of mixing media were prepared for 45 random remnant plasma samples: standard human plasma, control plasma N, previously analyzed patient with normal coagulation values, and home-made normal pool plasma (NPP). Samples were analyzed by using Siemens Dade Actin FSL Activated PTT Reagent on BCS XP analyzer. The median aPTT values of mixing studies with commercial lyophilized NPP, with commercial IQC, as well as with a patient did not differ (26.6, 26.3, and 26.8 s, respectively). Median value of a mixing study with home-made NPP was significantly higher from the rest of the group (27.9 s) ( P < 0.05). According to the obtained results, we decided to employ the commercial lyophilized NPP for future lupus anticoagulant mixing studies.