. 2020 Jul 25;48(9):612–618. doi: 10.1016/j.mpmed.2020.06.009

Table 3.

Blood and urine investigations in peripheral neuropathy

Initial ‘screening’ blood investigations

•
Full blood count and erythrocyte sedimentation rate
•
Renal, liver, bone and thyroid profiles
•
Fasting blood glucose and glycated haemoglobin
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Vitamin B₁₂ and folate
•
Serum protein electrophoresis, immunoglobulins and immunofixation
•
Antinuclear antibodies, double-stranded DNA antibodies, extractable nuclear antigens

Further blood investigations guided by mode of presentation

•
Suspected vasculitis – ANCA, hepatitis B and C serology, HIV, cryoglobulins, complement
•
Suspected infections – HIV (low threshold for testing), Lyme serology (if likely exposure)
•
Suspected hereditary neuropathy – chromosome 17 studies (duplication for CMT1A, deletion for HNPP). Mutations in specific genes: PMP22 and MPZ (CMT1), GJB1 (CMTX), MFN2 (20% of CMT2 patients). Gene panels and next-generation sequencing for rarer causes of Charcot–Marie–Tooth phenotype. White cell enzymes for inborn errors of metabolism. Gene analysis for familial amyloid polyneuropathy.
•
Specific auto-antibodies – antineuronal (paraneoplastic neuropathies), anti-GM1 ganglioside (MMN), anti-GQ1b ganglioside (MFS), anti-MAG (IgM paraproteinaemic neuropathy), paranodal (CIDP variants)
•
Other – angiotensin-converting enzyme (sarcoidosis), homocysteine and methylmalonic acid (functional vitamin B₁₂ deficiency), lipids and lipoproteins

Urine investigations in specific situations

•
Microscopy (for evidence of vasculitis)
•
Bence Jones proteinuria (for myeloma)
•
Porphyrins (hepatic porphyrias in the differential diagnosis of acute neuropathies)

ANCA, antineutrophil cytoplasmic antibodies; CMT1, autosomal dominant demyelinating Charcot–Marie–Tooth disease; HNPP, hereditary neuropathy with liability to pressure palsies; CMTX, X-linked Charcot–Marie–Tooth disease; CMT2, autosomal dominant axonal Charcot–Marie–Tooth disease; MMN, multifocal motor neuropathy; MFS, Miller Fisher syndrome; MAG, myelin-associated glycoprotein, CIDP, chronic inflammatory demyelinating polyradiculoneuropathy.