Investigations to determine aetiology of small fibre neuropathy. First line tests are determined by patient population and clinical suspicion.
| Blood tests | HBA1C, oral glucose tolerance test, urea and electrolytes, thyroid stimulating hormone, HIV serology, hepatitis C serology/viral load, ESR, ACE level, ANA, anti-Ro/La antibodies, rheumatoid factor/anticyclic citrullinated peptide antibodies, antitissue transglutaminase antibody, serum electrophoresis, vitamin B12 levels, leucocyte α-galactosidase A activity (Fabry's disease), lipid profile |
| Genetic testing | SCN9A/SCN10A mutations, transthyretin mutations (familial amyloid) |
| Imaging | If malignancy or sarcoidosis suspected chest X-ray/CT chest with contrast, SAP scan (amyloid) |
| Tissue biopsy | Abdominal fat biopsy (amyloid), small bowel biopsy (coeliac disease), biopsy of suspicious lesion to confirm malignancy, lip biopsy (Sjögren's syndrome), nerve biopsy is generally not performed unless there is large fibre involvement |
ESR, erythrocyte sedimentation rate; SAP, serum amyloid P component.