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23143 Myasthenia Gravis Evaluation, Pediatric (MGP1)

Myasthenia Gravis Evaluation, Pediatric (MGP1)
Test Code: MGPEDSO
Synonyms/Keywords
Ref Lab Code: 83371, Acetylcholine Receptor (Muscle AChR) Antibodies, AChR (Acetylcholine Receptor), Muscle End-Plate Antibodies, Myasthenia Gravis Antibodies, Myoid Antibody
Test Components
This test includes: ACh Receptor (Muscle) Binding Ab; ACh Receptor (Muscle) Modulating Ab.
Useful For
​Recommended for initial investigation of patients presenting at less than age 20 with a defect of neuromuscular transmission
 
Confirming that a recently acquired neurological disorder has an autoimmune basis
 
Distinguishing acquired Myasthenia Gravis from congenital myasthenic syndromes (persistently seronegative)
 
Providing a quantitative baseline for future comparisons in monitoring clinical course and response to immunomodulatory treatment
Specimen Requirements
Specimen Type Preferred Container/Tube Acceptable Container/Tube Specimen Volume Specimen Minimum Volume
(allows for 1 repeat)		 Pediatric Minimum Volume
(no repeat)
Serum​ Red Top Tube (RTT)​ Serum Separator Tube (SST)​ 2 mL​ 1.5 mL​ ​
Collection Processing Instructions
​ Patient should have no general anesthetic or muscle-relaxant drugs in the previous 24 hours.
Specimen Stability Information
Specimen Type Temperature Time
Serum​ ​ ​ Refrigerated​ 28 days​
Ambient ​ 72 hours​
Frozen​ ​28 days
Rejection Criteria
Gross hemolysis
​Gross lipemia
​Gross icterus
Performing Laboratory Information
Performing Location Day(s) Test Performed Analytical Time Methodology/Instrumentation
​Mayo Medical Laboratories
ACh receptor (muscle) binding antibody: Monday through Thursday; 6 p.m., Saturday; 10 a.m.
ACh receptor (muscle) modulating antibodies: Monday through Thursday; 11 a.m. ​
 3 days​
Radioimmunoassay (RIA)
​
Reference Lab
Mayo Clinic Laboratories
Reference Range Information
Interpretive report.
Interpretation
​Muscle acetylcholine receptor (AChR) autoantibodies are characteristic but not diagnostic of myasthenia gravis (MG). They are found in 13% of patients with Lambert-Eaton Syndrome (LES), which is rare in children. The patient's autoantibody profile is more informative than the result of any single test for supporting a diagnosis of MG.
 
Titers of AChR antibodies are generally higher in patients with severe weakness, but severity cannot be predicted by antibody titer. Seronegativity is more frequent in children with prepubertal onset of acquired MG (33%-50%) than in adults (<10%). Thymoma is rare under age 20, and striational antibodies (see STR/8746 Striational [Striated Muscle] Antibodies, Serum) also are rare, except in the context of MG related to neoplasia (usually thymoma or neuroblastoma), graft-versus-host disease, autoimmune liver disease, or D-penicillamine therapy. This laboratory has recently noted muscle-specific receptor tyrosine kinase antibody in children with "seronegative" acquired MG, but the frequency of this antibody in pediatric MG has not been determined.  
Outreach CPTs
CPT Modifier
(if needed)		 Quantity Description Comments
83519​ ​ 2​ ACh receptor antibody​ ​
Synonyms/Keywords
Ref Lab Code: 83371, Acetylcholine Receptor (Muscle AChR) Antibodies, AChR (Acetylcholine Receptor), Muscle End-Plate Antibodies, Myasthenia Gravis Antibodies, Myoid Antibody
Test Components
This test includes: ACh Receptor (Muscle) Binding Ab; ACh Receptor (Muscle) Modulating Ab.
Ordering Applications
Ordering Application Description
​Centricity ​Myasthenia Gravis Eval, Ped
​Cerner ​Myasthenia Gravis Eval, Pediatric (83371)
If the ordering application you are looking for is not listed, contact your local laboratory for assistance.
Specimen Requirements
Specimen Type Preferred Container/Tube Acceptable Container/Tube Specimen Volume Specimen Minimum Volume
(allows for 1 repeat)		 Pediatric Minimum Volume
(no repeat)
Serum​ Red Top Tube (RTT)​ Serum Separator Tube (SST)​ 2 mL​ 1.5 mL​ ​
Collection Processing
​ Patient should have no general anesthetic or muscle-relaxant drugs in the previous 24 hours.
Specimen Stability Information
Specimen Type Temperature Time
Serum​ ​ ​ Refrigerated​ 28 days​
Ambient ​ 72 hours​
Frozen​ ​28 days
Rejection Criteria
Gross hemolysis
​Gross lipemia
​Gross icterus
Useful For
​Recommended for initial investigation of patients presenting at less than age 20 with a defect of neuromuscular transmission
 
Confirming that a recently acquired neurological disorder has an autoimmune basis
 
Distinguishing acquired Myasthenia Gravis from congenital myasthenic syndromes (persistently seronegative)
 
Providing a quantitative baseline for future comparisons in monitoring clinical course and response to immunomodulatory treatment
Test Components
This test includes: ACh Receptor (Muscle) Binding Ab; ACh Receptor (Muscle) Modulating Ab.
Reference Range Information
Interpretive report.
Interpretation
​Muscle acetylcholine receptor (AChR) autoantibodies are characteristic but not diagnostic of myasthenia gravis (MG). They are found in 13% of patients with Lambert-Eaton Syndrome (LES), which is rare in children. The patient's autoantibody profile is more informative than the result of any single test for supporting a diagnosis of MG.
 
Titers of AChR antibodies are generally higher in patients with severe weakness, but severity cannot be predicted by antibody titer. Seronegativity is more frequent in children with prepubertal onset of acquired MG (33%-50%) than in adults (<10%). Thymoma is rare under age 20, and striational antibodies (see STR/8746 Striational [Striated Muscle] Antibodies, Serum) also are rare, except in the context of MG related to neoplasia (usually thymoma or neuroblastoma), graft-versus-host disease, autoimmune liver disease, or D-penicillamine therapy. This laboratory has recently noted muscle-specific receptor tyrosine kinase antibody in children with "seronegative" acquired MG, but the frequency of this antibody in pediatric MG has not been determined.  
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Performing Laboratory Information
Performing Location Day(s) Test Performed Analytical Time Methodology/Instrumentation
​Mayo Medical Laboratories
ACh receptor (muscle) binding antibody: Monday through Thursday; 6 p.m., Saturday; 10 a.m.
ACh receptor (muscle) modulating antibodies: Monday through Thursday; 11 a.m. ​
 3 days​
Radioimmunoassay (RIA)
​
Reference Lab
Mayo Clinic Laboratories
For billing questions, see Contacts
Outreach CPTs
CPT Modifier
(if needed)		 Quantity Description Comments
83519​ ​ 2​ ACh receptor antibody​ ​
For most current information refer to the Marshfield Laboratory online reference manual.