Anti-Sulfatide Antibodies

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Indications for measurement Interpretations of positive results Laboratory standards Antibody patterns: Specificity for sensory-motor neuropathies Clinical syndromes Demyelinating neuropathy Axonal neuropathy	Anti-Sulfatide antibodies: Summary of indications
	Indications Adult onset neuropathy: Clinical neuropathy features Distal Symmetric Sensory > Motor ↑ Likelihood of positive test Age > 50 Gait disorder Tremor Disability 2° sensory or motor loss Demyelination Serum IgM M-protein: 50% Lab standards 80% to 85% clinical specificity Interpretation of + result Diagnosis Dx of immune neuropathy Distinguish from CIDP Prognosis: Slow progression Treatment: ? HIG or cytoxan	Positive Results IgM vs Sulfatide > 10,000 + Low IgM vs Histone H3 + IgM M-protein Clinical correlation Sensory-motor neuropathy ± Gait Δ (GALOP) Demyelination Specificity: 85% IgM vs Sulfatide > 5,000 + Low IgM vs Histone H3 + No M-protein Clinical correlation Sensory neuropathy Axonal Specificity: 85% IgG vs Sulfatide > 6,000 + Low IgG vs GM1 Clinical correlation Sensory neuropathy Specificity: 80% IgM or IgG vs sulfatide between 1,500 and 5,000 Clinical correlation Abnormal but poor clinical correlation with neuropathies

Diagnostic work-up of symmetric polyneuropathy with prominent distal sensory loss.
Clinical features that increase probability of a positive result
1. Age > 50 years
2. Distal pain or paraesthesias in both feet and hands
3. Disability from motor or sensory loss
4. Gait disorder
5. Serum IgM M-protein
6. Demyelination without conduction block on electrodiagnostic studies.

Monoclonal IgM vs Sulfatide > 10,000 + Low IgM vs Histone H3
- Specificity: 85% for sensory-motor polyneuropathies with demyelinating features
- An associated gait disorder (GALOP syndrome) occurs in some patients
Polyclonal IgM vs Sulfatide > 6,000 + Low IgM vs Histone H3
- Specificity: 85% for sensory-motor neuropathies with axonal features.
Polyclonal IgG vs Sulfatide > 6,000 + Low IgG vs GM1 ganglioside
- Specificity: 80% for sensory-motor neuropathies with axonal features.

Commercially obtained sulfatide antigen must be additionally purified.
ELISA assays should use antibody binding periods > 5 hours at 4 degrees C.
Laboratories must document the sensitivity and specificity of anti-Sulfatide antibody testing by:
1. Technical comparison with known positive and negative serums.
2. Demonstrating that antibody binding is selective to sulfatide
  and not polyspecific to a wide variety of glycolipid antigens.
3. Clinical correlation with patients having sensory-motor neuropathies.

Diagnostic:
- May be only positive diagnostic test
  - This is especially helpful in patients whose neuropathy would otherwise be labeled as idiopathic.
- Provides independent support for a diagnosis of an immune-mediated sensory-motor or sensory polyneuropathy.
  - The neuropathy may be either demyelinating or axonal.
  - Suggests treatment possibilities when neuropathy is disabling
Prognostic:
- Suggests that the polyneuropathy will most often be slowly progressive over a period of years.
Treatment:
- Indicates directions for treatment in patients with disabling polyneuropathy
  - Some immunomodulating treatments, such as intravenous immunoglobulin or cyclophosphamide, may produce improvement in weakness, sensory loss or gait disability.
  - Corticosteroids are unlikely to be of benefit, even when neuropathy is demyelinating.

References
1. JNNP 1997;62:581-585