Purpose Venous thromboembolic (VTE) disease, which includes pulmonary embolism (PE) and deep vein thrombosis (DVT), remains a challenging diagnosis despite the development of non-invasive tests to help rule-out the disease. Several studies have found that a negative D-dimer can exclude VTE in low-risk patients. However, few studies have investigated the radiological findings of patients where a clinician has ordered imaging despite a negative D-dimer. This study attempts to determine the radiological diagnoses of patients who received imaging despite negative D-dimer tests.
Methods A retrospective chart review was performed including all patients who received a negative D-dimer test and a radiological study within 48 hours between February 1, 2002 and February 1, 2003. A radiological study included ventilation/perfusion scanning, computed tomography, vascular ultrasound, or pulmonary arteriogram. These studies were used to evaluate PE and DVT. All radiological studies were initially coded as negative, indeterminate, or positive. Patients with studies coded as indeterminate or positive, as well as those that had multiple studies associated with a single D-dimer test were re-reviewed by a senior chest radiologist for final classification. Inter-rater reliability was determined by a second senior radiologist for a randomly selected 25% representation of the population.
Results Two groups were identified for study, those with D-dimer values ≤350ng/mL (1) and those with values between 351-500ng/mL (2). Among the 3553 D-dimer tests ordered during the time period, 1362 were suitable for chart review in (1). Radiological studies were associated with 166 of these tests. 93.4% of the final radiological diagnoses were negative, 3.6% were indeterminate, and 3.0% (1.0-6.9%) were positive. In (2), 316 D-dimer tests were suitable for chart review and 89 were associated with radiological studies. 94.4% of the final radiological diagnoses were negative, 2.2% were indeterminate, and 3.4% (0.7-9.6%) were positive.
Conclusions A small proportion of patients who receive imaging despite negative D-dimer tests have positive radiological diagnoses.
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