Bruce L. Davidson, MD, MPH; Marc J. Lacrampe, MD
Potential Conflicts of Interest: Disclosures can be viewed at www.acponline.org/authors/icmje/ConflictOfInterestForms.do?msNum=M10-0344.
Requests for Single Reprints: Bruce L. Davidson, MD, MPH, 1952 Tenth Avenue West, Seattle, WA 98119; e-mail, email@example.com.
Current Author Addresses: Dr. Davidson: 1952 Tenth Avenue West, Seattle, WA 98119.
Dr. Lacrampe: Virginia Mason Medical Center, 1100 Ninth Avenue, Seattle, WA 98101.
Davidson BL, Lacrampe MJ. Why Can't Magnetic Resonance Imaging Reliably Diagnose Pulmonary Embolism?. Ann Intern Med. 2010;152:467-468. doi: 10.7326/0003-4819-152-7-201004060-00012
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Published: Ann Intern Med. 2010;152(7):467-468.
In this issue, the PIOPED III (Prospective Investigation of Pulmonary Embolism Diagnosis III) investigators report the results of their diagnostic accuracy study of magnetic resonance pulmonary angiography (MRA) and thigh-vein magnetic resonance venography (MRV) for identifying suspected pulmonary embolism (1). They conclude that combined MRA and MRV ought to be considered only at centers that perform it well and only in patients who have contraindications to other standard tests. We agree with their conclusions and the methods they used to reach them.
Not a management study, PIOPED III subjected patients with suspected pulmonary embolism to the clinical site's usual diagnostic testing—clinical suspicion assessment, d-dimer testing, and imaging tests—to arrive at a “reference standard” diagnosis for each patient, in whom pulmonary embolism was either confirmed, refuted, or uncertain. Then, all consenting patients with confirmed pulmonary embolism, as well as a sufficient number in whom it was refuted to allow for robust statistical test accuracy reporting, received combined MRA and MRV within 72 hours of presentation. The article's Table 3 (1) shows that 33 of 104 patients with pulmonary embolism had inadequate MRA or MRV and 6 of the 104 had adequate tests but, alas, false-negative results, for an overall sensitivity of only 63%. The patients with pulmonary embolism are the ones we would like to diagnose, not leave untreated. Looking solely at MRA, 17 of the 104 patients had false-negative results—1 pulmonary embolism patient in every 6—so it would be nearly impossible to rely on a normal result. After the study was planned, the investigators described (2) how subsequent clinical reports associated nephrogenic systemic and dermal fibrosis and renal failure with magnetic resonance contrast agents, resulting in the exclusion of patients with serum creatinine levels greater than 132.6 μmol/L (>1.5 mg/dL) for men and greater than 123.8 μmol/L (>1.4 mg/dL) for women and in exclusion of patients with estimated glomerular filtration rates less than 95 mL/min per 1.73 m2 (men) and less than 75 mL/min per 1.73 m2 (women). Even patients with end-stage renal disease were excluded, because although their renal function might not worsen after use of the contrast agents, they could develop lethal systemic fibrosis (3).
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Emergency Medicine, Pulmonary/Critical Care, Venous Thromboembolism, Pulmonary Embolism.
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Print ISSN: 0003-4819 | Online ISSN: 1539-3704
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