A normal Silica Clotting Time (SCT) ratio (<1.20) indicates that a lupus anticoagulant (LA) is not present  or not detectable  by this method (but might be detected with other methods).   Because of the heterogeneous nature of LA antibodies  no single coagulation test can identify or exclude all LA. Currently  the International Society on Thrombosis and Hemostasis and the Clinical and Laboratory Standards Institute (CLSI) recommend testing for LA with at least 2 phospholipid-dependent clotting time assays based on different coagulation pathways and principles (e.g; SCT and dRVVT).   Abnormal SCT ratio (SCT ratio ≥1.20) may suggest the presence of LA; however  other possibilities include:  -Coagulation factor deficiencies  -Other types of coagulation factor inhibitors  -Anticoagulation therapy effects (NOTE: testing at least 1 week from discontinuation of anticoagulation therapy is recommended)   The diagnosis of LA requires evidence of persistence of a positive LA over time (≥12 weeks). Repeat SCT testing after at least 12 weeks is recommended to confirm the diagnosis.