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Polymorphisms of several clotting factors have been associated during the past few years with an increased risk of both venous or arterial thrombosis. However, final proof for the existence of a pathogenetic relationship between a given polymorphism and an increased risk for thrombosis is still lacking.

SummaryTissue thromboplastin inhibition assay (TTI) is a sensitive test for lupus anticoagulant (LA). We have performed TTI in 12 LA positive patients using a new recombinant human tissue factor (Innovin, IN) and compared it with Thromborel S (TH), a commonly used human placenta thromboplastin. The effect of using two different dilutions of each thromboplastin (1:10 & 1:26) was investigated. A 1:26 dilution discriminated better than the 1:10 and this was more evident for Innovin. The mean value obtained with a 1:26 IN dilution was statistically different from that observed with TH at the same dilution. Furthermore when PT and TTI ratios were considered, differences were statistically significant and seemed to increase depending on thromboplastin dilutions. When we used IN at 1:26 all LA positive patients had a value > 1.2. Then we compared TTI at a 1:26 dilution with dilute Russell's Viper Venom Time (dRVVT) in 50 consecutive patients with suspected lupus anticoagulant not treated with warfarin or heparin. In these patients the diagnosis of lupus anticoagulant was carried out using dilute APTT mixing studies and a platelet neutralization procedure: four out of 50 patients thus tested were LA positive. When dRVVT or TTI‐I 1:26 were used, five patients were positive for lupus anticoagulant. Innovin showed similar sensitivity of dRVVT for detection of lupus anticoagulant. It is likely that higher dilutions of thromboplastins could further improve the specificity of this method.

Camporese G, Bernardi E, Scarano L, Ghirarduzzi A, Imberti D and Prandoni P, on behalf of The PALIST Study Group. Outcome of patients with suspected lower limb symptomatic deep vein thrombosis and a normal ultrasound‐based initial diagnostic workup: a prospective study. J Thromb Haemost2012; 2605–6.