Although a d-dimer level has a high sensitivity and negative predictive value, it has very low specificity and positive predictive value. It is of little use in ruling out high-risk patients. d-dimer levels have been reported to be normal in 25% of patients without PE, a number that is likely significantly lower in postoperative patients.100 Therefore, this laboratory test should not be used to rule out PE in postoperative urologic surgery patients. A ventilation-perfusion (V/Q) scan is interpreted on the

basis of pretest clinical probability. In patients with high clinical probability and high probability V/Q scan, a 95% positive predictive value has been reported. A 96% negative predictive Inhibitors,research,lifescience,medical value has been described in low probability patients. However, the combination of clinical and scan probability generally ranges from 15% to 86% for most patients. Therefore, further evaluation may be required in a large portion of patients who

have undergone a V/Q scan.101 The Inhibitors,research,lifescience,medical rationale behind the use of lower extremity compression ultrasound in the evaluation of suspected PE is Inhibitors,research,lifescience,medical that a positive study will prompt essentially the same management as if PE were detected without subjecting patients to radiation, radiocontrast, or an invasive study. However, a negative study does not rule out PE and requires further evaluation for PE specifically. This phenomenon is particularly problematic because the rate of negative lower extremity ultrasounds in the setting of PE has been reported to be 71%.102 Some have advocated complete lower extremity compression ultrasonography or serial exams for 2 weeks after suspected PE with low probability V/Q scans to decrease false-negative rates.103–107 Although the results of Inhibitors,research,lifescience,medical these studies have been encouraging, it is the opinion of the buy Palbociclib authors that PE represents too dangerous a clinical entity to

safely observe without instituting therapy except in the rare instance where anticoagulation poses more of a Inhibitors,research,lifescience,medical threat to the patient’s health than PE. The most widely used study for the definitive diagnosis of PE is spiral computed tomography scan. The advantages of this study include a high specificity, widespread availability, noninvasiveness, rapidity of the procedure, and ability to diagnose other pathologic processes potentially GBA3 responsible for clinical presentation. Disadvantages are few, but include potential for contrast nephropathy as well as contraindication in renal insufficiency and in patients with contrast allergy. Reported sensitivity has varied drastically and seems to be related to experience of the interpreting radiologist as well as pretest probability. In the largest study to date, the use of the Well’s Criteria to stratify patients into high, intermediate, and low clinical probability improved both positive and negative predictive values substantially. Accuracy appears to be equal to V/Q scan.