Three milliliters (3 ml) of venous blood were collected within the first 24 h post ICU admission. Blood samples were either collected in red topped Vacutainer tubes (BD, Mississauga, Ontario,Canada) in order to collect serum, or in Vacutainer tubes containing either 0.129 M (3.8%) trisodium citrate or EDTA for the collection of plasma. Whole blood was allowed to clot by leaving it undisturbed at room temperature for 15–30 min. Serum was collected after centrifugation at 1000g for 10 min at 4Celcious, apportioned into 0.5 ml aliquots, and stored at -80C until used. Alternatively,the citrate or EDTA-containing tubes were centrifuged for 10 min at 1000g at 4C to remove cells from plasma. Subsequently, plasma was collected, apportioned into 0.5 ml aliquots and stored at
-80 Celcious until used.