Diagnostic accuracy of silica clotting time method for lupus anticoagulant in a clinical population with various symptoms of antiphospholipid syndrome

• Published in: Lupus 2016-04, Vol.25 (4), p.418-422
• Main Authors: Averina, M, Johannesen, S, Brox, J
• Format: Article
• Language: English
• Subjects: Adult; Antibodies; Anticoagulants; Antiphospholipid syndrome; Antiphospholipid Syndrome - blood; Antiphospholipid Syndrome - complications; Antiphospholipid Syndrome - diagnosis; Antiphospholipid Syndrome - immunology; Area Under Curve; Autoimmune diseases; Biomarkers - blood; Blood Coagulation; Cardiolipin; Case-Control Studies; Clotting; Female; Humans; Lupus; Lupus Coagulation Inhibitor - blood; Male; Methods; Middle Aged; Partial Thromboplastin Time - methods; Partial Thromboplastin Time - standards; Population; Predictive Value of Tests; Prothrombin Time; Reference Values; Reproducibility of Results; Rheumatic diseases; ROC Curve; Silica; Silicon Dioxide; Systemic lupus erythematosus; Venom
• ISSN: 0961-2033; 1477-0962
• DOI: 10.1177/0961203315617540

Introduction: Correct interpretation of lupus anticoagulant (LA) tests is crucial for diagnosis of antiphospholipid syndrome (APS). This study assessed diagnostic accuracy of the SCT method in a clinical population with various symptoms of APS. Material and methods: Altogether 60 APS patients were consecutively recruited from a relevant clinical population. All cases had stable positivity of at least one of the reference tests (two other LA methods; anticardiolipin- and anti-β2-glycoprotein-I antibodies). Controls (n = 62) with negative reference tests were also consecutively recruited from the same clinical population. Results and conclusions: Receiver operator characteristic (ROC) analysis for the SCT test to identify the APS cases showed area under the curve of 0.82 (95% CI 0.75–0.90). The positive cut-off defined by a non-parametric method (99 percentile in a healthy population) had specificity of 92%, but low sensitivity of 53%. The optimal cut-off corresponded to the 97.5 percentile (67% sensitivity and 92% specificity). Combined sensitivity of the positive diluted Russell Viper Venom time (dRVVT) and SCT tests was 73%, while specificity remained 92%. The sensitivity of the SCT method varied in different clinical subgroups and was highest in patients with rheumatic diseases and in patients with triple positivity of three reference methods.