Factor VIII, IX, and XI measurement by one-stage clotting assay with silica clotting time confirm reagent: a clinical laboratory helpful tool in the presence of lupus anticoagulant

Introduction: In clinical practice, coagulation factors levels measurement is used to detect possible factor deficiency in patients with bleeding manifestations or to explain the origin of prolonged routine coagulation tests results. Objectives: The aim was to evaluate factor VIII (FVIII), factor IX (FIX), and Factor XI (FXI) assay performed with silica clotting time confirm (SCTC) reagent in LA positive (AL+), normal controls (NC), and factors deficient (D) samples. Materials and methods: Citrated plasmas: 73 AL+, 45 NC; 77 D: 40 FVIII, 22 FIX, and 15 FXI. FVIII, FIX, and FXI D. (1) SynthASil activated partial thromboplastin time (APTT) (SYNT); (2) SCTC (3) FVIII chromogenic assay (FVIIICHROM). Results: NC: slightly lower FVIIISCTC than FVIIISYNT and FIXSYNT than FIXSCTC. No differences FXISYNT versus FXISCTC. D: No differences between FVIIISCTC, FVIIISYNT, and FVIIICHROM, or FXISYNT versus FXISCTC. FIX SYNT is slightly higher than FIXSCTC. NC+C: FVIII, FIX and FXI SCTC-SYNT r > 0.970. AL+: 36.7% FVIIISYNT, 66.1% FIXSYNT, and 86.2% FXISYNT nonparallel dilution curves. FVIIISYNT1/40, FVIIISCTC, and FVIII: CHROM comparable results. FVIIISCTC-FVIIICHROM, r: 0.949, FVIIISCTC-FVIIISYNT, r: 0.759. Low FIXSCTC-FIXSYNT, no correlation FXISCTC-FXISYNT. Conclusion: FVIII, FIX, and FXI assays with SCTC seem to be useful to measure factor levels in AL+ samples.