Recommended Tests for Diagnosing Low Back Pain
For most patients with low back pain, diagnostic testing is not routinely recommended, as a focused history and physical examination are sufficient for initial evaluation and management. 1, 2
Initial Diagnostic Approach
- Begin with a focused history and physical examination to categorize patients into one of three groups: nonspecific low back pain (85% of cases), back pain with radiculopathy or spinal stenosis, or back pain potentially associated with a specific spinal cause 1, 2
- The history should include assessment of psychosocial risk factors that predict risk for chronic disabling back pain 1, 2
- Screen for "red flags" that may indicate serious underlying conditions requiring prompt evaluation 2, 3:
- History of cancer (positive likelihood ratio 14.7) 2
- Unexplained weight loss (positive likelihood ratio 2.7) 2
- Failure to improve after 1 month (positive likelihood ratio 3.0) 2
- Age older than 50 years (positive likelihood ratio 2.7) 2
- Fever or recent infection 2, 4
- Significant trauma relative to age 2, 4
- Progressive neurologic deficits 1, 2
- Bladder or bowel dysfunction (cauda equina syndrome) 2, 4
Imaging Recommendations
- Do not routinely obtain imaging or other diagnostic tests for nonspecific low back pain 1
- Perform diagnostic imaging when 1:
- Severe or progressive neurologic deficits are present
- Serious underlying conditions are suspected based on history and physical examination
- For patients with persistent low back pain and signs/symptoms of radiculopathy or spinal stenosis, use MRI (preferred) or CT only if they are potential candidates for surgery or epidural steroid injection 1
- Plain radiography is recommended for initial evaluation of possible vertebral compression fracture in higher-risk patients (history of osteoporosis or steroid use) 1
Specific Testing Based on Suspected Diagnosis
- For suspected malignancy: Consider plain radiography or erythrocyte sedimentation rate (ESR) measurement (a rate ≥20 mm/h has 78% sensitivity and 67% specificity for cancer) 1
- MRI is recommended for patients with a history of cancer, which is the strongest predictor of vertebral cancer 1
- For suspected infection: Consider ESR, C-reactive protein, and complete blood count 5, 4
- For suspected cauda equina syndrome: Immediate MRI is indicated 1, 4
- For suspected radiculopathy: Neurologic examination to assess for motor weakness, sensory deficits, and reflex changes 2, 5
Caveats and Pitfalls
- Routine imaging can lead to unnecessary interventions and identify radiographic abnormalities poorly correlated with symptoms 1
- Absence of red flags does not meaningfully decrease the likelihood of serious pathology; 64% of patients with spinal malignancy had no associated red flags in one study 6
- Some red flags (such as night pain) may have high false-positive rates for serious conditions like infection 6
- Plain radiography exposes patients to ionizing radiation; a single lumbar spine radiograph (2 views) exposes young women to gonadal radiation equivalent to daily chest radiographs for more than 1 year 1
- Thermography and electrophysiologic testing are not recommended for evaluation of nonspecific low back pain 1
Follow-up Assessment
- Reevaluate patients with persistent, unimproved symptoms after 1 month 1
- Consider earlier or more frequent reevaluation for patients with severe pain, functional deficits, older age, or signs of radiculopathy or spinal stenosis 1
- For patients with risk factors for cancer but no signs of spinal cord compression, several diagnostic strategies have been proposed, but none have been prospectively evaluated 1