META: an MRI-based scoring system differentiating metastatic from osteoporotic vertebral fractures

Magnetic resonance imaging (MRI) is useful for the differential diagnosis of osteoporotic vertebral fractures (OVFs) and metastatic vertebral fractures (MVFs), but no single finding is absolutely conclusive.

The purpose of the present study was to create a scoring system to facilitate the correct diagnosis of MVFs by integrating several MRI findings.

This is a retrospective and single-center observational study that attempts to create a diagnostic scoring system by discriminant analysis.

We included 100 OVFs and 100 MVFs in thoracolumbar vertebrae of which MR images were obtained within 60 days from the suspected time of fractures.

The sensitivity and specificity of known important MRI findings were assessed, and the classification accuracy of the scoring system was investigated.

Seven MRI findings of these fractures were analyzed to evaluate their sensitivity and specificity. Using these findings as variables, discriminant analysis was performed in 140 fractures as a training set, and the classification accuracy was calculated in the remaining 60 fractures as a test set. Additionally, the images of these 60 fractures were reviewed by another blinded reviewer to investigate the interobserver reliability of each finding.

All findings had high specificity with low-to-moderate sensitivity. Eight variables were selected in the final discriminant function. A simpler scoring system (MRI Evaluation Totalizing Assessment [META]) was created by approximating the coefficients and the constant term by integral numbers. The classification accuracy was calculated to be 96.6% in the test set. The interobserver reliability of the key findings varied, but the final discrimination conducted by META had the high agreement between the two reviewers (κ=0.93).

This novel scoring system, META, could prove to be a useful tool for the differential diagnosis of OVFs and MVFs. It is simple and physician friendly, yet highly accurate.