Ans. b (D-dimer assay) (Ref. H - 18th/ch. 116)The quantitative plasma D-dimer ELISA level is elevated (>500 ng/mL) in more than 90% of patients with Pulmonary Embolism, reflecting plasmin's breakdown of fibrin and indicating endogenous (though clinically ineffective) thrombolysis. However, the D-dimer assay is not specific and therefore has no useful role among patients who are already hospitalized. Levels increase in patients with myocardial infarction, sepsis, or almost any systemic illness. The plasma D-dimer ELISA has a high negative predictive value and can be used to help exclude PE. Dimer often elevated in patients withvenous thrombosis. It is a sensitive, but not specific, test for venous thrombosis.DISSEMINATED INTRAVASCULAR COAGULATION (DIC)# Activation of coagulation cascade leading to microthrombi and global consumption of platelets, fibrin, and coagulation factors.# Causes- Obstetric complications (most common cause),- Gram-negative sepsis,- Transfusion,- Trauma,- Malignancy,- Acute pancreatitis,- Nephrotic syndrome,# Lab findings- | PT,- | PIT,- | fibrin split products (D-dimers),- | platelet count.- "Helmet-shaped cells and schistocytes" on blood smear.# The quantitative plasma D-dimer enzyme-linked immunosorbent assay (ELISA) level is elevated (>500 ng/mL) in more than 90% of patients with pulmonary embolism, reflecting plasmin's breakdown of fibrin and indicating endogenous (though clinically ineffective) thrombolysis.# However, the D-dimer assay is not specific and levels increase in patients with myocardial infarction, aortic dissection, sepsis, or almost any systemic illness.0# The plasma D-dimer ELISA has a high negative predictive value and can be used to help exclude Pulm embolism, for which it serves as AN EXCELLENT SCREENING TEST, with a sensitivity of 96.4% and negative predictive value of 99.6%.