In the normal range (70-130%), only moderate decreases in AT have been reported to be associated with thrombosis.16-18 The overall much higher frequency of protein S deficiency (16.6%), which was four times greater than in Western studies14,15 could be partly attributed to reductions in C4b protein, as a result of higher rates of subclinical infections among Indians. Here, PROS1 is linked to Venous thrombosis.