Essential Questions for Diagnosing Low Back Pain
To establish a clear diagnosis of low back pain, clinicians should conduct a thorough diagnostic triage by asking about pain characteristics, red flags, and psychosocial factors that may influence outcomes. 1, 2
Pain Characteristics and History
- Ask about location of pain, frequency of symptoms, and duration of pain, as well as any history of previous symptoms, treatment, and response to treatment 1
- Determine if pain is axial (localized to back), radicular (radiating down leg in nerve root distribution), or referred from non-spinal sources 3
- For patients with leg pain, inquire about typical sciatica symptoms (back and leg pain in a typical lumbar nerve root distribution) 1
- For suspected spinal stenosis, ask about pseudoclaudication (leg pain with walking/standing relieved by sitting) and whether pain is relieved by sitting 1
Red Flag Assessment
- Screen for cauda equina syndrome: urinary retention (90% sensitivity), fecal incontinence, saddle anesthesia, and motor deficits at multiple levels 1, 4
- Screen for malignancy: history of cancer (positive likelihood ratio 14.7), unexplained weight loss (positive likelihood ratio 2.7), failure to improve after 1 month (positive likelihood ratio 3.0), and age older than 50 years (positive likelihood ratio 2.7) 1, 4
- Screen for spinal infection: fever, recent infection, intravenous drug use, and immunocompromised status 1, 4
- Screen for vertebral compression fracture: older age, history of osteoporosis, and steroid use 1
- Consider ankylosing spondylitis in younger patients with morning stiffness, improvement with exercise, alternating buttock pain, and awakening due to back pain during the second part of the night 1
- Consider non-spinal sources of pain such as pancreatitis, nephrolithiasis, aortic aneurysm, or systemic illnesses 1
Neurological Assessment
- For patients with radicular symptoms, assess knee strength and reflexes (L4 nerve root), great toe and foot dorsiflexion strength (L5 nerve root), foot plantarflexion and ankle reflexes (S1 nerve root), and distribution of sensory symptoms 1
- Document any rapidly progressive or severe neurologic deficits, including motor deficits at more than one level 1
Psychosocial Factors
- Assess psychosocial factors and emotional distress as they are stronger predictors of low back pain outcomes than either physical examination findings or severity and duration of pain 1
- Screen for depression, passive coping strategies, job dissatisfaction, higher disability levels, disputed compensation claims, or somatization, as these may predict poorer outcomes 1
- Consider using screening tools to predict progression from acute to chronic low back pain 5
Diagnostic Categorization
- Based on history and examination, categorize patients into one of three diagnostic groups: nonspecific low back pain, back pain potentially associated with radiculopathy or spinal stenosis, or back pain potentially associated with another specific spinal cause 1, 2
- Recognize that nonspecific low back pain is defined as "pain occurring primarily in the back with no signs of a serious underlying condition, spinal stenosis, radiculopathy, or another specific spinal cause" 2
- Note that degenerative changes on imaging often correlate poorly with symptoms and are usually considered nonspecific 2
Common Pitfalls to Avoid
- Avoid routine imaging for nonspecific low back pain as it does not improve outcomes and may expose patients to unnecessary radiation 1
- Do not delay imaging when red flags are present; immediate MRI is indicated rather than waiting the usual 4-6 weeks recommended for nonspecific back pain 4
- Remember that cauda equina syndrome is rare (prevalence 0.04% among patients with low back pain) but requires immediate intervention to prevent permanent disability 4
- Be aware that the posttest probability of cancer increases from approximately 0.7% to 9% in patients with a history of cancer presenting with back pain 4