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Meta-analysis: Accuracy of Contrast-Enhanced Magnetic Resonance Angiography for Assessing Steno-occlusions in Peripheral Arterial Disease

Jan Menke, MD; and Jörg Larsen, MD
[+] Article, Author, and Disclosure Information

From University Hospital and Evangelisches Krankenhaus, Goettingen, Germany.

Potential Conflicts of Interest: None disclosed. Forms can be viewed at www.acponline.org/authors/icmje/ConflictOfInterestForms.do?msNum=M10-0907.

Corresponding Author: Jan Menke, MD, Diagnostic Radiology, University Hospital, Robert-Koch-Strasse 40, 37075 Goettingen, Germany; e-mail, Menke-J@T-Online.de.

Current Author Addresses: Dr. Menke: Diagnostic Radiology, University Hospital, Robert-Koch-Strasse 40, 37075 Goettingen, Germany.

Dr. Larsen: Clinical Radiology, Evangelisches Krankenhaus, An der Lutter 24, 37075 Goettingen, Germany.

Author Contributions: Conception and design: J. Menke.

Analysis and interpretation of the data: J. Menke, J. Larsen.

Drafting of the article: J. Menke, J. Larsen.

Critical revision of the article for important intellectual content: J. Menke, J. Larsen.

Final approval of the article: J. Menke, J. Larsen.

Statistical expertise: J. Menke.

Collection and assembly of data: J. Menke, J. Larsen.

Ann Intern Med. 2010;153(5):325-334. doi:10.7326/0003-4819-153-5-201009070-00007
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Background: Contrast-enhanced magnetic resonance angiography (MRA) is a noninvasive, radiation-free imaging method for studying peripheral arterial disease (PAD) of the lower extremities.

Purpose: To summarize evidence of prospective studies about how well MRA identifies or excludes arterial steno-occlusions (50% to 100% lumen reduction) in adults with PAD symptoms.

Data Sources: PubMed and 3 other databases were searched from 1998 to 2009 without language restrictions.

Study Selection: Two independent reviewers selected 32 studies that compared MRA with intra-arterial digital subtraction angiography in PAD. Eligible studies were prospective and provided data to reconstruct 2 × 2 or 3 × 3 contingency tables (<50% stenosis vs. ≥50% stenosis or occlusion of arterial segments) in at least 10 patients with PAD symptoms.

Data Extraction: Two reviewers independently assessed the study quality and extracted the study data, with disagreements resolved by consensus.

Data Synthesis: The 32 included studies generally had high methodological quality. About 26% of the 1022 included patients had critical limb ischemia with pain at rest or tissue loss. Overall, the pooled sensitivity of MRA was 94.7% (95% CI, 92.1% to 96.4%) and the specificity was 95.6% (CI, 94.0% to 96.8%) for diagnosing segmental steno-occlusions. The pooled positive and negative likelihood ratios were 21.56 (CI, 15.70 to 29.69) and 0.056 (CI, 0.037 to 0.083), respectively. Magnetic resonance angiography correctly classified 95.3%, overstaged 3.1%, and understaged 1.6% of arterial segments.

Limitation: Similar to most studies of computed tomographic angiography in PAD, the primary studies reported the diagnostic accuracy of MRA on a per-segment basis, not a per-patient basis.

Conclusion: This meta-analysis of 32 prospective studies further increases the evidence that contrast-enhanced MRA has high accuracy for identifying or excluding clinically relevant arterial steno-occlusions in adults with PAD symptoms.

Primary Funding Source: None.


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Figure 2.
Summary of quality of 32 studies assessed by using the QUADAS tool.

The consensus judgment of both readers is shown as cumulative percentages across the 32 primary studies. QUADAS = Quality Assessment of Diagnostic Accuracy Studies.

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Appendix Figure.
Meta-analytic summary plots based on MRA studies of the entire arterial tree.

MRA = magnetic resonance angiography; PAD = peripheral arterial disease. Circles represent individual studies. The area of each study's circle is inversely proportional to the study size. The plus sign represents the bivariate summary estimate of the random-effects meta-analysis, and the surrounding ellipse shows the corresponding bivariate 95% CI. The likelihood ratio profile (left) shows that MRA is a suitable method for either confirming or excluding relevant arterial steno-occlusions in patients with PAD symptoms. The bivariate plot of sensitivity and specificity (right) visualizes the generally high sensitivity and specificity of MRA in PAD and also indicates that MRA is a suitable method for either confirming or excluding steno-occlusive disease. The bowed curve is the summary receiver-operating characteristic curve, and the colored areas correspond to the colored quadrants in the likelihood ratio profile. Both plots are closely related by the following equations: Positive likelihood ratio = sensitivity ÷ (1 − specificity) Negative likelihood ratio = (1 − sensitivity) ÷ specificity Sensitivity = [positive likelihood ratio − (positive likelihood ratio × negative likelihood ratio)] ÷ (positive likelihood ratio − negative likelihood ratio) Specificity = (positive likelihood ratio − 1) ÷ (positive likelihood ratio − negative likelihood ratio)

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Figure 3.
Conditional probabilities based on MRA studies of the entire arterial tree.

The x-axis represents the pretest probability of having segmental PAD of the lower extremities on the basis of clinical findings before the index test (contrast-enhanced MRA). The y-axis represents the posttest probability of having segmental PAD. Conditional on the pretest probability, the upper curve shows the percentage of true-positive results among all positive MRA findings (positive predicted value) and the lower curve shows the percentage of false-negative results among all negative MRA findings (1 − negative predictive value). Patients with positive MRA findings (upper curve) are much more likely to have PAD than those with negative MRA findings (lower curve). These conditional probability curves are meant for orientation and are based on the summary estimates of the meta-analysis for the entire arterial tree. The surrounding bands represent 95% CIs. MRA = magnetic resonance angiography; PAD = peripheral arterial disease.

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