Background: The accuracy of gadolinium-enhanced magnetic resonance pulmonary angiography and magnetic resonance venography for diagnosing pulmonary embolism has not been determined conclusively.
Objective: To investigate performance characteristics of magnetic resonance angiography, with or without magnetic resonance venography, for diagnosing pulmonary embolism.
Design: Prospective, multicenter study from 10 April 2006 to 30 September 2008.
Setting: 7 hospitals and their emergency services.
Patients: 371 adults with diagnosed or excluded pulmonary embolism.
Measurements: Sensitivity, specificity, and likelihood ratios were measured by comparing independently read magnetic resonance imaging with the reference standard for diagnosing pulmonary embolism. Reference standard diagnosis or exclusion was made by using various tests, including computed tomographic angiography and venography, ventilation-perfusion lung scan, venous ultrasonography, d-dimer assay, and clinical assessment.
Results: Magnetic resonance angiography, averaged across centers, was technically inadequate in 25% of patients (92 of 371). The proportion of technically inadequate images ranged from 11% to 52% at various centers. Including patients with technically inadequate images, magnetic resonance angiography identified 57% (59 of 104) with pulmonary embolism. Technically adequate magnetic resonance angiography had a sensitivity of 78% and a specificity of 99%. Technically adequate magnetic resonance angiography and venography had a sensitivity of 92% and a specificity of 96%, but 52% of patients (194 of 370) had technically inadequate results.
Limitation: A high proportion of patients with suspected embolism was not eligible or declined to participate.
Conclusion: Magnetic resonance pulmonary angiography should be considered only at centers that routinely perform it well and only for patients for whom standard tests are contraindicated. Magnetic resonance pulmonary angiography and magnetic resonance venography combined have a higher sensitivity than magnetic resonance pulmonary angiography alone in patients with technically adequate images, but it is more difficult to obtain technically adequate images with the 2 procedures.
Trial registration: ClinicalTrials.gov NCT00241826.