<s>[INST] context: (D-dimer) (266-70-CMDT-10) (1653-H17th)D-dimer serves as an excllant screening test with a sensitivity of 96.4% and negative predictive value of 99.6% but only for out patient or emergency department patients, not for hospitalized patients (1562-H16th)PULMONARY VENOUS THROMBOEMBOLISM (PE)Laboratory findings* ECG - Most common abnormality are sinus tachycardia*** Arterial blood gases - reveal acute respiratory alkalosis due to hyperventilation* Plasma level of D-dimer - using a D- dimmer threashold between 300 and 500 ng/ml, a rapid quantitative ELISA has shown a sensitivity for venous thromboembolism of 95-97% and a specificity of 45%. Therefore a D-dimer >500 ng/ml using the rapid ELISA provides strong evidence against venous thrmboembolism with a likehood ratio of 0.11 -0.13* Serum troponin I, troponin T, and beta natriuretic peptide (BNP) levels are increased* CT - helical CT pulmonary angiography has essentially supplanted V/Q scanning as the initial diagnostic study in North America for suspected PE (Proximal pulmonary variety)* Pulmonary angiography - remains the reference gold standard for the diagnosis of PE**** Best investigation when there is clinical suspicion of pulmonary embolism in a patient is - Multi detector CT angiogrphy**1. Increased D-dimer values are associated with(a) DIC (secondary fibrinolysis)(b) Arterial or venous thrombosis (Deep vein thrombosis)(c) Renal or liver failure(d) Pulmonary embolism(e) Late in pregnancy preclampsia(f) Myocardial infarction(g) Malignancy inflammation and severe infection2. D- dimmer values are increased with tPA anticoagulant therapy3. D- dimmer assay is not specific* CT of the chest with intravenous contrast is the principal imaging test for diagnosis of pulmonary empolism (1654-H17th)* Lung scanning is now second-line diagnostic test for PE {Mostly used for patients who cannot tolerate intravenous contrast) [/INST] question: Most important screening test in pulmonary thromboembolism is | options: A: D-dimer B: X-rays C: ECG D: Angiography | answer: A </s>