What are the sensitivity and specificity of the various diagnostic tests used to document a herniated lumbar disc? How often are they abnormal in individuals without low back pain?
The diagnostic tests used to evaluate low back pain have the following sensitivity and specificity in patients with surgically documented herniated lumbar discs causing a compressive radiculopathy:
Sensitivity (%) | Specificity (%) | |
|---|---|---|
| Electromyography | 92 | 83 |
| CT scans | 92 | 88 |
| Myelography | 90 | 87 |
| MRI scans | 93 | 92 |
It is important to note that a significant number of asymptomatic individuals without low back pain will have an abnormal CT scan or myelogram (30%–40%). MRI studies have shown that 25% to 50% of individuals without low back pain will have a disc bulge or protrusion at one or more lumbar disc levels. Consequently, disc bulges/protrusions on MRI in patients with low back pain are usually coincidental, whereas disk extrusion, especially with compression of the lumbar nerve, is usually a significant cause of radicular back pain.
