Patient comes with burning sensation in feet what tests should be done
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"burning feet" OR "burning foot" diagnosis workup
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"peripheral neuropathy" diagnosis evaluation
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Investigations for Burning Sensation in Feet
Burning feet is most commonly a manifestation of peripheral neuropathy - particularly small-fiber neuropathy. The workup proceeds from a structured history and examination to targeted labs, then electrophysiology and specialized tests.
Step 1: History-Directed Approach
Before ordering tests, identify key features:
- Duration and onset (acute vs. subacute vs. chronic)
- Distribution (feet only, stocking-glove, asymmetric)
- Associated symptoms: weakness, autonomic symptoms, gait unsteadiness
- Risk factors: diabetes, alcohol use, medications, occupational toxin exposure, family history
Step 2: First-Line Laboratory Tests (Screening)
These are recommended for all patients with unexplained peripheral neuropathy / burning feet:
| Test | Reason |
|---|---|
| Fasting blood glucose + HbA1c | Diabetes - most common cause |
| CBC | Anaemia, infection |
| ESR / CRP | Vasculitis, inflammatory disorders |
| Serum Vitamin B12 | B12 deficiency neuropathy |
| Thyroid-Stimulating Hormone (TSH) | Hypothyroid neuropathy |
| Urea, Creatinine (BUN/Cr) | Uraemic neuropathy |
| Liver Function Tests (LFTs) | Alcohol-related liver disease / nutritional deficiency |
| Serum Vitamin B1, B3, B6 | Nutritional deficiency neuropathies ("burning feet syndrome") |
"If the cause of neuropathy is not obvious, some screening laboratory studies should be considered, including ESR, CBC, LFTs, and determination of fasting blood glucose, glycosylated hemoglobin, BUN, creatinine, serum vitamin B12, and TSH levels." - Textbook of Family Medicine, 9e, p.1242
Step 3: Electrophysiological Studies
EMG + Nerve Conduction Studies (NCS) - order early:
- Confirm peripheral neuropathy and define the type of fibers involved (sensory, motor, or both)
- Distinguish axonal loss from demyelination
- Identify entrapment neuropathies
- Limitation: NCS are most useful for large-fiber disease. In pure small-fiber neuropathy (which classically causes burning feet), NCS may be completely normal - this does NOT rule out neuropathy
Step 4: Second-Line Tests (Based on Clinical Suspicion)
Order these after reviewing initial results:
| Test | When to Order |
|---|---|
| Serum protein electrophoresis (SPEP) / UPEP | Paraproteinaemia, myeloma |
| ANA, anti-dsDNA, SSA/SSB | SLE, Sjögren syndrome (pure small-fiber neuropathy) |
| ANCA, cryoglobulins | Vasculitic neuropathy |
| HIV serology | HIV neuropathy (small-fiber type) |
| RPR/VDRL | Syphilis |
| Anti-ganglioside antibodies | GBS, CIDP |
| Heavy metal screen (arsenic, thallium, lead) | Toxic neuropathy |
| Urine porphyrins | Porphyria |
| Serum ACE, chest X-ray | Sarcoidosis |
| Genetic testing (CMT panel) | Hereditary neuropathy if family history |
| CSF (LP) | Elevated protein with normal WBC suggests GBS or CIDP |
Step 5: Specialized Tests for Small-Fiber Neuropathy
When NCS is normal but burning symptoms persist:
| Test | Purpose |
|---|---|
| Skin punch biopsy (intraepidermal nerve fiber density, IENFD) | Gold standard for small-fiber neuropathy diagnosis |
| Quantitative sensory testing (QST) | Thermal discrimination thresholds (heat/cold) |
| Vibration sensation thresholds (VST) | Subclinical large-fiber involvement |
| Autonomic function tests | Sudomotor testing (QSART), tilt table |
| Corneal confocal microscopy | Non-invasive measure of corneal nerve fiber density |
Step 6: Nerve / Muscle Biopsy (Last Resort)
Reserved for cases suspected of:
- Vasculitis
- Amyloidosis
- Leprosy
- Sarcoidosis
- Demyelinating disorders (CIDP)
Typically uses the sural nerve (lateral heel/ankle). Not done routinely due to risk of permanent dysaesthesia.
Common Causes to Rule Out Systematically
| Cause | Key Test |
|---|---|
| Diabetes mellitus | Fasting glucose, HbA1c |
| Vitamin B12/B1/B3 deficiency | Serum levels |
| Hypothyroidism | TSH |
| Chronic kidney disease | Creatinine, BUN |
| Alcohol abuse | LFTs, GGT, B1 levels |
| Vasculitis / connective tissue disease | ANA, ANCA, cryoglobulins |
| HIV | HIV serology |
| Paraproteinaemia | SPEP, UPEP |
| Idiopathic small-fiber neuropathy | Skin biopsy (IENFD) |
In up to 50% of patients, even after extensive evaluation, no cause is found - termed cryptogenic sensory polyneuropathy (CSPN). - Harrison's Principles of Internal Medicine, 22e
Sources:
- Textbook of Family Medicine, 9e (pp. 1242-1243)
- Harrison's Principles of Internal Medicine, 22e
- Adams and Victor's Principles of Neurology, 12e
- Bradley and Daroff's Neurology in Clinical Practice
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