Test Catalog

Test Id : ACMFS

Acetylcholine Receptor Modulating Antibody, Flow Cytometry Assay, Serum

Useful For
Suggests clinical disorders or settings where the test may be helpful

Diagnosis for autoimmune myasthenia gravis (MG) in adults and children

 

Distinguishing autoimmune from congenital MG in adults and children or other acquired forms of neuromuscular junction transmission disorders.

 

This test is a qualitative assay and should not be used for monitoring purposes.

Method Name
A short description of the method used to perform the test

Only orderable as part of a profile. For more information see:

MGLE / Myasthenia Gravis/Lambert-Eaton Myasthenic Syndrome Evaluation, Serum

MGMR / Myasthenia Gravis Evaluation with Muscle-Specific Kinase (MuSK) Reflex, Serum

PAVAL / Paraneoplastic, Autoantibody Evaluation, Serum

 

Flow Cytometry

NY State Available
Indicates the status of NY State approval and if the test is orderable for NY State clients.

Yes

Reporting Name
Lists a shorter or abbreviated version of the Published Name for a test

AChR Modulating Flow Cytometry, S

Aliases
Lists additional common names for a test, as an aid in searching

Acetylcholine receptor modulating antibody

AChR modulating antibody

Specimen Type
Describes the specimen type validated for testing

Serum

Ordering Guidance

Typically, physicians will order acetylcholine receptor (AChR) binding, blocking, and modulating antibodies. Mayo Clinic Laboratories' (MCL) tests are not named in that manner; instead these are offered as myasthenia gravis (MG) evaluations. MGMR / Myasthenia Gravis Evaluation with Muscle-Specific Kinase (MuSK) Reflex, Serum is the testing of choice in most cases.

 

AChR blocking antibody testing is no longer offered individually as it offers no added-value to the diagnosis and management of MG.

Specimen Required
Defines the optimal specimen required to perform the test and the preferred volume to complete testing

Only orderable as part of a profile. For more information see:

MGLE / Myasthenia Gravis/Lambert-Eaton Myasthenic Syndrome Evaluation, Serum

MGMR / Myasthenia Gravis Evaluation with Muscle-Specific Kinase (MuSK) Reflex, Serum

PAVAL / Paraneoplastic, Autoantibody Evaluation, Serum

 

Container/Tube:

Preferred: Red top

Acceptable: Serum gel

Specimen Volume: 1 mL

Specimen Minimum Volume
Defines the amount of sample necessary to provide a clinically relevant result as determined by the Testing Laboratory

0.5 mL

Reject Due To
Identifies specimen types and conditions that may cause the specimen to be rejected

Gross hemolysis Reject
Gross lipemia Reject
Gross icterus Reject

Specimen Stability Information
Provides a description of the temperatures required to transport a specimen to the performing laboratory, alternate acceptable temperatures are also included

Specimen Type Temperature Time Special Container
Serum Refrigerated (preferred) 28 days
Frozen 28 days
Ambient 72 hours

Useful For
Suggests clinical disorders or settings where the test may be helpful

Diagnosis for autoimmune myasthenia gravis (MG) in adults and children

 

Distinguishing autoimmune from congenital MG in adults and children or other acquired forms of neuromuscular junction transmission disorders.

 

This test is a qualitative assay and should not be used for monitoring purposes.

Clinical Information
Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

Fatigable weakness due to impaired postsynaptic transmission at the neuromuscular junction is characteristic of myasthenia gravis (MG). A clinical diagnosis should be supported by electrodiagnostic testing, ie, clinical-electrodiagnosis (EDX). Positive autoimmune serology increases certainty of MG diagnosis but needs to be interpreted in the proper clinical-EDX context with response to anticholinesterase medications supporting the diagnosis. Most cases are autoimmune and are caused by IgG autoantibodies binding to critical postsynaptic membrane molecules (nicotinic muscle acetylcholine receptor [AChR] or its interacting proteins, such as muscle-specific kinase [MuSK]). Serologically, the detection of AChR binding antibody provides the best diagnostic sensitivity. However, the presence of both AChR binding and modulating activity improves diagnostic accuracy. Autoantibody detection frequency is lowest in patients with weakness confined to extraocular muscles (72% are positive for AChR binding antibodies) and highest in patients with generalized weakness due to MG (92% are positive for AChR binding antibodies). In adults with MG and AChR antibodies, approximately 20% will have thymoma and very rarely (<1%) extrathymic cancers. Computed tomography (CT) imaging of the chest is considered the standard of care to evaluate for thymoma.

 

These results should only be interpreted in the appropriate clinical and electrophysiological context and are not diagnostic in isolation.

 

Note: Single antibody tests may be requested in the follow-up of patients with positive results previously documented in this laboratory.

Reference Values
Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

Only orderable as part of a profile. For more information see:

MGLE / Myasthenia Gravis/Lambert-Eaton Myasthenic Syndrome Evaluation, Serum

MGMR / Myasthenia Gravis Evaluation with Muscle-Specific Kinase (MuSK) Reflex, Serum

PAVAL / Paraneoplastic, Autoantibody Evaluation, Serum

 

Negative

Interpretation
Provides information to assist in interpretation of the test results

This assay shows strong qualitative concordance with the previous modulating assay.

 

Positive results in this antibody evaluation are indicative of autoimmune myasthenia gravis (MG). These results should be interpreted in the appropriate clinical and electrophysiological context.

 

The presence of acetylcholine receptor (AChR) modulating antibodies along with AChR binding antibodies as compared to AChR binding antibodies alone, improves the diagnostic accuracy for MG.

 

In the presence of AChR modulating antibodies, a paraneoplastic basis should be considered with thymoma being the most commonly associated tumor with MG.

 

Negative results do not exclude the diagnosis of MG. If clinical suspicion remains and symptoms persistent or worsen consider re-testing.

Cautions
Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

Positive results are found in some patients with Lambert-Eaton syndrome (LES), paraneoplastic central nervous system (CNS) and peripheral nervous system (PNS) autoimmune disorders and in healthy individuals.

 

Hemolysis, muscle-relaxant drugs used in the course of general anesthesia, or serum exposed to high ambient temperature can cause false-positive results.

Clinical Reference
Recommendations for in-depth reading of a clinical nature

1. Lozier BK, Haven TR, Astill ME, Hill HR: Detection of acetylcholine receptor modulating antibodies by flow cytometry. Am J Clin Pathol. 2015 Feb;143(2):186-192

2. Keefe D, Hess D, Bosco J, et al: A rapid, fluorescence-based assay for detecting antigenic modulation of the acetylcholine receptor on human cell lines. Cytometry B Clin Cytom. 2009 May;76(3):206-212

Method Description
Describes how the test is performed and provides a method-specific reference

This method uses flow cytometry to measure the loss of acetylcholine receptors (AChR) expressed on the surface of live cells. The cell line used is an immortalized human rhabdomyosarcoma cell line that expresses endogenous muscle-type nicotinic AChR on its surface. Cells are plated in a 96-well plate and cultured prior to the addition of patient serum, which is then incubated on the cells to enable antibody-mediated internalization of AChR (modulation).

 

Subsequently, modulation is then stopped and the amount of AChR on the cell surface is measured by flow cytometry. The detection of receptors is performed using a recombinant rat monoclonal antibody specific for the human alpha-subunit of the AChR followed by a secondary goat anti-rat IgG antibody conjugated with allophycocyanin (APC). The amount of AChR on the cell surface is proportional to the median fluorescence intensity (MFI) of APC. To calculate the amount of modulation (ie, % loss of AChR), the APC MFI is compared between cells treated with patient serum and cells treated with serum lacking AChR modulating antibodies. Background signal is established in each experiment utilizing cells stained with secondary antibody alone (no patient sera). The percent loss of AChR is calculated as 1-([Patient MFI-Background MFI]/[Negative calibrator MFI-Background MFI]*100%).(Unpublished Mayo method)

PDF Report
Indicates whether the report includes an additional document with charts, images or other enriched information

No

Day(s) Performed
Outlines the days the test is performed. This field reflects the day that the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time before the test is performed. Some tests are listed as continuously performed, which means that assays are performed multiple times during the day.

Monday, Wednesday, Saturday

Report Available
The interval of time (receipt of sample at Mayo Clinic Laboratories to results available) taking into account standard setup days and weekends. The first day is the time that it typically takes for a result to be available. The last day is the time it might take, accounting for any necessary repeated testing.

5 to 8 days

Specimen Retention Time
Outlines the length of time after testing that a specimen is kept in the laboratory before it is discarded

28 days

Performing Laboratory Location
Indicates the location of the laboratory that performs the test

Rochester

Fees
Several factors determine the fee charged to perform a test. Contact your U.S. or International Regional Manager for information about establishing a fee schedule or to learn more about resources to optimize test selection.

  • Authorized users can sign in to Test Prices for detailed fee information.
  • Clients without access to Test Prices can contact Customer Service 24 hours a day, seven days a week.
  • Prospective clients should contact their Regional Manager. For assistance, contact Customer Service.

Test Classification
Provides information regarding the medical device classification for laboratory test kits and reagents. Tests may be classified as cleared or approved by the US Food and Drug Administration (FDA) and used per manufacturer instructions, or as products that do not undergo full FDA review and approval, and are then labeled as an Analyte Specific Reagent (ASR) product.

This test was developed, and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the US Food and Drug Administration.

CPT Code Information
Provides guidance in determining the appropriate Current Procedural Terminology (CPT) code(s) information for each test or profile. The listed CPT codes reflect Mayo Clinic Laboratories interpretation of CPT coding requirements. It is the responsibility of each laboratory to determine correct CPT codes to use for billing.

CPT codes are provided by the performing laboratory.

86255

LOINC® Information
Provides guidance in determining the Logical Observation Identifiers Names and Codes (LOINC) values for the order and results codes of this test. LOINC values are provided by the performing laboratory.

Test Id Test Order Name Order LOINC Value
ACMFS AChR Modulating Flow Cytometry, S 99062-2
Result Id Test Result Name Result LOINC Value
Applies only to results expressed in units of measure originally reported by the performing laboratory. These values do not apply to results that are converted to other units of measure.
610029 AChR Modulating Flow Cytometry, S 99062-2

Test Setup Resources

Setup Files
Test setup information contains test file definition details to support order and result interfacing between Mayo Clinic Laboratories and your Laboratory Information System.

Excel | Create a PDF

Sample Reports
Normal and Abnormal sample reports are provided as references for report appearance.

Normal Reports | Abnormal Reports

SI Sample Reports
International System (SI) of Unit reports are provided for a limited number of tests. These reports are intended for international account use and are only available through MayoLINK accounts that have been defined to receive them.

SI Normal Reports | SI Abnormal Reports