| LABORATORY TESTING: SERUM ANTIBODIES | |||||||
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Indications Lower motor neuron syndromes Motor neuropathy: Chronic; Acute Clinical features Distal; Asymmetric Upper extremity onset: Often Treatment follow-up Document sufficient cytoxan Best prognosis: Anti-GM1 titers ê by > 70% é Likelihood of positive test: Asymmetry No upper motor neuron signs No prominent sensory Δ Motor conduction block + Results ELISA IgM vs GM1 or NP-9 > 1,800 Low IgM vs Histone H3 IgG vs GM1 > 1,000 Low IgG vs Sulfatide Clinical correlations IgM + Motor neuropathy: Chronic 85% sensitivity 99% specificity vs ALS IgG + Motor neuropathy: Acute 50% sensitivity 90% specificity Lab standards: IgM > 80% sensitivity for MMN > 95% clinical specificity Interpretation Diagnosis Dx of immune neuropathy Distinguish vs CIDP & ALS Prognosis: Not ALS; Slow progression Treatment Cytoxan or HIG often useful Prednisone not useful Follow-up: Cytoxan Rx é anti-GM1 titer ® ? Relapse |
Indications Adult onset neuropathy: Clinical: Distal; Symmetric; Sensory > Motor Electrodiagnostic: Demyelination Usually with é distal latency No conduction block Serum: IgM M-protein Treatment follow-up Document sufficient cytoxan Best prognosis: Anti-MAG titers ê by > 60% Usually with cytoxan Rx é Likelihood of positive test: Age > 50 Gait disorder Tremor Disability 2° sensory or motor loss Demyelination Serum IgM M-protein: 85% + Results ELISA IgM vs MAG > 1,500 Low IgM vs Histone H3 Western blot confirmation Clinical correlation: Titer > 6,000 Demyelinating neuropathy 90% specificity; 95% sensitivity Lab standards Document 90% clinical specificity Interpretation Diagnosis Dx of immune neuropathy Distinguish from CIDP Prognosis: Slow progression Treatment Cytoxan may be useful Prednisone & HIG not useful Follow-up é anti-MAG titer ® ? Relapse |
Indications Adult onset neuropathy: Clinical: Distal; Symmetric; Sensory > Motor é Likelihood of positive test: Age > 50 Gait disorder Tremor Disability 2° sensory or motor loss Demyelination Serum IgM M-protein: 50% + Results IgM vs Sulfatide > 5,000 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% Lab standards 80% to 85% clinical specificity Interpretation Diagnosis Dx of immune neuropathy Distinguish from CIDP Prognosis: Slow progression Treatment: ? HIG or cytoxan |
Indications Sensory neuronopathy é Likelihood of positive test: Asymmetry; Rapid progression Sensory ê: Proximal; All modalities CNS signs: Cerebellar; Limbic Neoplasm: Small cell lung Low likelihood of positive test: Sensory neuropathy Distal only; Chronic Normal proprioception Weakness: Distal + Result Clinical correlation Low titer: Neoplasm High titer: Also PNS & CNS Δ Specificity > 95% Lab standards 2 methods confirm IgG vs Hu Western blot: 35 to 40 kDa bands Immunocytochemistry IgG vs neuronal nuclei Interpretation Neuronopathy: No response to Rx Neoplasm: Small cell Work-up indicated Small size; Slow-growing |
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Yo: Cerebellar; Female Ca Tr: Cerebellar; Hodgkin's Ri: Opsoclonus; Ataxia; Breast Ca GQ1b: Miller-Fisher (80%) GalNAc-GD1a: AMAN; Demyelinating PN GAD: Stiffman; Diabetes Tubulin: IgM; CIDP; Asymmetry GD1b: IgM; Ataxic neuropathy P-type Ca++ channel: LEMS Striation: MG; Thymoma K+ channel (KCNA6): Isaac's Decorin (BJ): Myopathy; IgM Jo-1: Myositis; Lung Δ Mi-2: Dermatomyositis; Nail Δ ANCA: Vasculitis SSA (Ro): Sjögren's | |||||||
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Indications Neuropathy & Gait Δ Onset > 50 Sensory ± motor PN Gait Δ; Falling + Result IgM vs GALOP antigen > 10,000 Low IgM vs Histone H3 Specificity > 90% Interpretation Diagnosis Dx of immune neuropathy Distinguish from CIDP Prognosis: Slow progression Treatment: HIG or cytoxan |
Indications Adult-onset neuropathy Clinical: Numerous syndromes + Result IgM, IgG, or IgA M-protein Lab standards Immunofixation method NOT protein electrophoresis Interpretation Diagnosis r/o Myeloma Skeletal survey ± Bone marrow biopsy |
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| Laboratory standard testing | |||
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Neuromuscular Clinical Lab Washington University 660 South Euclid Box 8111 St. Louis, MO 63110 314-362-6981 Testing: GM1; MAG; Sulfatide Hu; Yo; GALOP; BJ |
Oklahoma Medical Research Foundation Clinical Immunology Laboratory 825 N.E. 13th Street, C-323 Oklahoma City OK 73104 405-271-7771 Testing: Myositis antibodies |
Athena Diagnostics Four Biotech Park 377 Plantation Street Worcester, MA 01605 800-394-4493 Testing: Sulfatide; GALOP; Hu & Yo (Western blot only); CMT 1A & X |
Mayo Medical Lab 200 First Street SW Rochester, Minnesota 55905 800-533-1710 Testing: AChR antibody; LEMS antibody; Hu (Immunocytochemistry only) |