Introduction: Antiphospholipid antibody syndrome (APS) is an important cause for idiopathic thrombotic events especially in young patients. Failure to recognize APS and initiate prompt treatment leads to considerable morbidity and mortality. There are only very few studies in Asian population on the significance of APS in the evaluation of idiopathic thrombosis. Here we describe the association of different APS tests with thrombotic events in Indian population. Method: The study was conducted at a Government Medical College in North Kerala, India. All patients who presented to the medicine department with arterial or venous thrombosis as the manifestation of APS during a two-year period were studied. Anticardiolipin (aCL) and anti β2 glycoprotein (antiβ2G) both IgG and IgM tests were done on patients at presentation and 12 weeks later. Higher of the two values were taken for analysis in relation to clinical manifestations. Patient was considered to be positive for aCL test if the titer was more than 40 GPL or MPLfor IgG and IgM aCL tests respectively. Antiβ2G is considered to be positive if the titer is more than 40U/ml for IgG or IgM antiβ2G tests. Lupus anticoagulant test was done by dRVVT (dilute Russel Viper Venom Time) test. Results: The study population included 77 patients, with majority (58%) between 20 and 40 years. There is statistically significant association between aCL IgG and occurrence of total arterial events (p =0.0059,r= 0.622) and also for stroke (p=0.03) and myocardial infarction (MI) (p=0.01). There is also significant association between aCL IgM positivity and occurrence of total arterial events (p =0.0004) and MI (p =0.05), but not for stroke. There is also strong association between both antiβ2G isotypes and MI. LA test also showed significant relation with total arterial events (p =0.0024), stroke (p =0.049) and MI (p =0.05). Conclusions: This study highlights the importance of testing for APS in young patients with idiopathic thrombosis. The concept of triple positivity in APS has also been emphasized by our study
