A highly sensitive quantitative immunoassay to measure the concentration of D-dimer in blood plasma. D-dimer is a fibrin degradation (breakdown) product that forms when blood clotting occurs and then dissolves. Elevated levels are an indicator of acute and ongoing thrombosis (blood clotting) in the body, making it a valuable test for ruling out thrombotic conditions such as Pulmonary Embolism (PE) and Deep Vein Thrombosis (DVT).