A diagnostic systematic review

MRI is currently the imaging modality of choice to investigate conditions causing low back pain (LBP). In about 95% of cases LBP is non-specific, however it may also be caused by a serious pathology such as lumbar disc herniation, spinal stenosis, tumors, fractures, infections, etc.

The aim of this systematic review was to quantify the diagnostic accuracy of MRI to identify serious pathologies causing LBP. Eight studies were included and when possible, data was included in a meta-analysis and pooled. The gold standard were findings at surgery, expert panel opinion or diagnostic work up.

Simply put, high sensitivity refers to correctly identifying all the patients with the condition, high specificity refers to correctly excluding patients without the condition.
– Herniated nucleus pulposus (HNP): (bulge, protrusion, extrusion or sequestration of nucleus pulposus). The sensitivity of MRI to correctly identify these pathologies was 75%, specificity was 77%.
– Nerve root compression (“sciatica”) caused by HNP: Sensitivity was high (81-92%), with varying specificity (52-100%).
– Spinal stenosis: MRI was highly sensitive (87-96%) but moderately specific (68-75%).

In conclusion, these poor results show that non-negligible numbers of LBP patients will be incorrectly diagnosed when MRI is used in isolation. Clinically, it is recommended that MRI should be used in combination with other observations and tests, so as to best inform clinical reasoning and decision-making > From Wassenaar et al., Eur Spine J 21 (2012) 220-227. All rights reserved to Springer-Verlag.

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