There were five trauma cases this morning in the ICU. The ICU 2 was admitted during the weekend. Another polytrauma case (without TBI), who developed acute respiratory failure and required ventilatory support. The injuries are fracture right ribs from 2nd to 5th, lung contusion, open book fracture and fracture femur. The C-spine was cleared clinically. There were bilateral pulmonary infiltrates on both sides of the lungs. He has moderate increased in A-a gradient. I start to go thru few differential diagnoses in my mind which include fat embolism syndrome, PE, aspiration pneumonia, worsening lung contusions and finally TRALI. Suddenly I was distracted by the MO's comment: Since the D-dimer was positive, this patient has been treated for pulmonary embolism and 'they' have started him on fondaparinux...I asked, what was the next plan? She said, the orthopedic team is planning for ILN once this patient is more 'stable'..Actually, I raised few issues, first of all the safety of fondaparinux in this pelvic injury and secondly since when D-dimer was used as a confirmatory test for PE??
"D-dimer assays for the diagnosis of PE have been extensively studied. They are best characterized as having good sensitivity and negative predictive value but poor specificity and positive predictive value."
Sensitivity: D-dimer levels are abnormal in about 95% of all patients with PE when measured by ELISA, quantitative rapid ELISA or semi-quantitative rapid ELISA. This falls to about 90% when measured by qualitative rapid ELISA or quantitative latex agglutination, 86% measured by semiquantitative latex agglutination and 82% measured by erythrocyte agglutination. Among patients who have subsegmental PE, d-dimer levels are abnormal in only 50% when measured by quantitative latex agglutination.
Specificity: D-dimer levels are normal in only 40-68% of patients without PE, regardless of the assay used. This is a consequence of abnormal D-dimer levels being common among hospitalized patients, especially those with malignancy or recent surgery. The specificity decreases even further in the setting of severe renal dysfunction and increased patient age.
NPV: The ability of a normal or negative D-dimer assay to exclude acute PE depends on both the type of D-dimer assay and the clinical pretest probability that a patient has acute PE.
Taken together, the evidence indicates that a D-dimer level less than 500ng/ml by quantitative ELISA or semiquantitative latex agglutination is sufficient to exclude PE in patients with a low or moderate pretest probability of PE.
source: uptodate.com
"D-dimer assays for the diagnosis of PE have been extensively studied. They are best characterized as having good sensitivity and negative predictive value but poor specificity and positive predictive value."
Sensitivity: D-dimer levels are abnormal in about 95% of all patients with PE when measured by ELISA, quantitative rapid ELISA or semi-quantitative rapid ELISA. This falls to about 90% when measured by qualitative rapid ELISA or quantitative latex agglutination, 86% measured by semiquantitative latex agglutination and 82% measured by erythrocyte agglutination. Among patients who have subsegmental PE, d-dimer levels are abnormal in only 50% when measured by quantitative latex agglutination.
Specificity: D-dimer levels are normal in only 40-68% of patients without PE, regardless of the assay used. This is a consequence of abnormal D-dimer levels being common among hospitalized patients, especially those with malignancy or recent surgery. The specificity decreases even further in the setting of severe renal dysfunction and increased patient age.
NPV: The ability of a normal or negative D-dimer assay to exclude acute PE depends on both the type of D-dimer assay and the clinical pretest probability that a patient has acute PE.
Taken together, the evidence indicates that a D-dimer level less than 500ng/ml by quantitative ELISA or semiquantitative latex agglutination is sufficient to exclude PE in patients with a low or moderate pretest probability of PE.
source: uptodate.com
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