Diagnostic accuracy of magnetic resonance imaging for an acute pulmonary embolism: results of the 'IRM-EP' study.
BACKGROUND
Magnetic resonance imaging (MRI) has not been validated as an alternative diagnostic test to computed tomography angiography (CTA) in patients with suspicion of a pulmonary embolism (PE).


OBJECTIVE
To evaluate performance of current MRI technology in diagnosing PE, in reference to a 64-detector CTA.


METHODS
Prospective investigation including 300 patients with a suspected PE, referred for CTA after assessment of clinical probability and D-dimer testing. MRI protocol included unenhanced, perfusion and angiographic sequences. MRI results were interpreted by two independent readers, to evaluate inter-reader agreement. Sensitivity and specificity were evaluated globally and according to PE location and to clinical probability category.


RESULTS
Of 300 enrolled patients, 274 were analyzed and 103 (37.5%) had a PE diagnosed by CTA. For patients with conclusive MRI results (72% for reader 1, 70% for reader 2), sensitivity and specificity were 84.5% (95% confidence interval [CI], 74.9-91.4%) and 99.1% (95% CI, 95.1-100.0%), respectively, for reader 1, and 78.7% (95% CI, 68.2-87.1%) and 100% (95% CI, 96.7-100.0%) for reader 2. After exclusion of inconclusive MRI results for both readers, inter-reader agreement was excellent (kappa value: 0.93, 95% CI: 0.88-0.99). Sensitivity was better for proximal (97.7-100%) than for segmental (68.0-91.7%) and sub-segmental (21.4-33.3%) PE (P < 0.0001). Sensitivity was similar for both readers within each clinical probability category.


CONCLUSIONS
Current MRI technology demonstrates high specificity and high sensitivity for proximal PE, but still limited sensitivity for distal PE and 30% of inconclusive results. Although a positive result can aid in clinical decision making, MRI cannot be used as a stand-alone test to exclude PE.
Department of Radiology, Hôpital Européen Georges Pompidou, APHP, Paris, France. marie-pierre.revel@htd.aphp.fr
M P
MP
Revel
O
O
Sanchez
S
S
Couchon
B
B
Planquette
A
A
Hernigou
R
R
Niarra
G
G
Meyer
G
G
Chatellier
D000208:Acute Disease; D000328:Adult; D000368:Aged; D016009:Chi-Square Distribution; D003287:Contrast Media; D005260:Female; D005602:France; D006785:Hospitals, University; D006801:Humans; D019028:Magnetic Resonance Imaging, Cine; D008297:Male; D008875:Middle Aged; D061330:Multidetector Computed Tomography; D015588:Observer Variation; D055420:Perfusion Imaging / Q000379:methods*; D011237:Predictive Value of Tests; D011446:Prospective Studies; D011655:Pulmonary Embolism / Q000175:diagnosis* / Q000000981:diagnostic imaging; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
D003287:Contrast Media