PB0876 - Significance of Anti-Beta2-Glycoprotein and Anti-Cardiolipin antibodies added to CMC LA algorithm in various clinical settings.

Background: Anti Phospholipid Antibody (APLA) is one of the most common acquired thrombophilias. Lupus anticoagulant (LAC) testing has various issues due to varied sensitivities of clot-based assays. As a minor deviation from standard LA algorithm, Christian Medical College (CMC) LA algorithm starts with DRVVT (Dilute Russell’s viper venom time) Screen Mix.

Aims: To study the significance of CMC LA algorithm in combination with antibodies to β2-glycoprotein I (anti-β2-GPI) and cardiolipin (aCL) towards the diagnosis of APLA, and to compare CMC LA algorithm with guideline-based LA algorithm.

Methods: This was a retrospective study for a period of 2 months where electronic medical records of 120 patients referred for LAC testing along with anti-β2-GPI and aCL results were reviewed. DRVVT (Stago, Paris, France) was done by CMC LA algorithm.

Results: 120 patients were referred for LAC test in view of arterial thrombosis (14%), venous thrombosis (32.5%), bad obstetric history (12.5%), connective tissue disorder (26%), other causes (14%). DRVVT positivity was seen in 15 cases (13%)- mild positivity in 9, moderate in 4 and marked in 2 cases. In DRVVT positive patients, triple positivity was seen in 4 out of 15 cases. CMC algorithm was equally effective to the guideline-based algorithm. There was one case where screen mix was more prolonged than screen, which would have been missed if we had employed guideline-based algorithm. In DRVVT negative patients, IgG anti-β2-GPI was negative in all cases, IgM anti-β2-GPI was positive in 9/105 (8%) cases and IgG aCL in 2/105 (1.9%). The sensitivity and specificity of the tests are shown in Table 1.

Conclusion(s): DRVVT has lower sensitivity but higher specificity in the various clinical scenarios compared. CMC LA algorithm was not only equally effective to guideline-based algorithm in picking up such cases but could also avoid missing one positive case.