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ANTI-Hu ANTIBODIES: Testing

• Diagnostic work-up of sensory ganglionopathy
  • Usually with proximal & distal sensory loss
• Clinical features that increase probability of a positive result (Up to 50%)
  • Onset
    • Asymmetric
    • Rapidly progressive
  • Sensory loss
    • All modalities, including proprioception
    • Proximal
  • Associated CNS signs
    • Cerebellar: Nystagmus; Dysmetria
    • Encephalopathy
  • Neoplasm: Especially small cell lung
• Clinical features that make a positive result unlikely (< 1 in 1,000)
  • Sensory loss: Distal only; No proprioceptive involvement
  • Slow progression over > 2 months
  • Motor involvement

• Usual: Positive result confirmed by 2 methods
  • Immunocytochemistry:
    • Selective staining of neuronal nuclei
  • Western blot vs. CNS nuclear proteins:
    • Staining of characteristic 35 to 40 kDa bands
• Also acceptable:
  • Positive result by: Immunocytochemistry
    • Test serums adsorbed with systemic antigens
    • Selective staining of neuronal nuclei
    • Laboratory must have strong clinical validation showing specificity and sensitivity of results
  • Positive result by: Western blot vs. recombinant Hu antigen
    • Staining of protein band
    • Control for each serum showing staining is specific
    • Laboratory must have strong clinical validation showing specificity and sensitivity of results

• Diagnostic
  • Any positive result
    • Indicates high likelihood of associated neoplasm: Especially small cell lung
  • High titer positive result: Strong specificity for
    • Sensory neuronopathy
    • Autonomic neuropathy
    • Cerebellar syndrome
    • Limbic encephalitis
• Prognostic
  • Neuronopathy is unlikely to respond to immunomodulating medications
  • Associated neoplasm is often small or slow growing