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Extended Myositis Panel

3001781

Extended Myositis Panel 3001781

Method

Semi-Quantitative Enzyme-Linked Immunosorbent Assay/Qualitative Immunoprecipitation/Semi-Quantitative Multiplex Bead Assay/Qualitative Immunoblot

May be useful for differential evaluation of polymyositis, dermatomyositis, necrotizing autoimmune myopathy, or overlap syndromes associated with connective tissue disease

Myositis is characterized by inflammation of the skeletal muscles involved in movement.^, The detection of antibodies may help to establish a diagnosis, aid in prognosis, and support treatment decisions.

Disease Overview

Myositis may occur in a number of inflammatory myopathies, including polymyositis/antisynthetase syndrome, dermatomyositis, necrotizing autoimmune myopathy, and sporadic inclusion body myositis, as well overlap syndromes with connective tissue disease.^, The primary symptom of all forms of myositis is progressive muscle weakness that may develop over a period of weeks, months, or years.^, Other symptoms may include joint pain and fatigue.^,

Antibody testing for myositis should be considered after a standard workup for inflammatory myopathies because it may aid in distinguishing between myopathies,^, which can have important implications for therapy and prognosis.

Refer to the ARUP Consult Inflammatory Myopathies – Myositis topic for more information about myositis and the typical testing strategy for inflammatory myopathies.

Test Description

This antibody panel test may be useful for the evaluation of patients with progressive proximal muscle weakness and/or other clinical findings suggestive of polymyositis/antisynthetase syndrome, dermatomyositis, necrotizing autoimmune myopathy, or overlap syndromes associated with connective tissue disease. Clinical phenotypes for specific antibody-associated inflammatory myopathies often overlap, and targeted panels allow for rapid identification of associated antibodies. Use of the most targeted panel, ie, the panel that most closely matches the patient’s complete clinical phenotype, is recommended:

Additional ARUP Myositis Panels
ARUP Panel to Consider	Clinical Utility
Dermatomyositis and Polymyositis Panel 3001783 Includes a subset of the antibodies on this panel that are specific to dermatomyositis and polymyositis	May be useful for the evaluation of patients with progressive proximal muscle weakness and/or with cutaneous manifestations suggestive of dermatomyositis and/or associated connective tissue disease
Polymyositis Panel 2013990 Includes a subset of the antibodies on this panel that are specific to polymyositis	May be useful for the evaluation of patients with progressive proximal muscle weakness and antisynthetase syndrome
Dermatomyositis Autoantibody Panel 3001782 Includes a subset of the antibodies on this panel that are specific to dermatomyositis	May be useful for the evaluation of patients with characteristic cutaneous manifestations of dermatomyositis with or without muscle weakness
Interstitial Lung Disease Autoantibody Panel 3001784 Antibodies overlap with the antibodies on this panel Refer to the Interstitial Lung Disease Autoantibody Panel Test Fact Sheet for more information	May be useful for the evaluation of patients with interstitial lung disease with or without other signs and symptoms of myositis

Antibodies Tested

This panel detects a selection of antibodies specific to or associated with myositis. For more information about the clinical associations with each of these antibodies, visit the ARUP Consult Inflammatory Myopathies – Myositis topic.

Extended Myositis Panel: Antibodies Detected and Methodology
Myositis-Associated Abs
Antibody	Method
Fibrillarin (U3 RNP) Ab, IgG	Qualitative immunoblot
Ku Ab	Qualitative immunoprecipitation
PM/Scl-100 Ab, IgG	Qualitative immunoblot
SSA-52 (Ro52) (ENA) Ab, IgG	Semiquantitative multiplex bead assay
SSA-60 (Ro60) (ENA) Ab, IgG	Semiquantitative multiplex bead assay
Smith/RNP (ENA) Ab, IgG	Semiquantitative multiplex bead assay
Myositis-Specific Abs^a
Dermatomyositis Abs^b
Antibody	Method
MDA5 (CADM-140) Ab	Qualitative immunoblot
Mi-2 (nuclear helicase protein) Ab	Qualitative immunoprecipitation
NXP2 (nuclear matrix protein-2) Ab	Qualitative immunoblot
P155/140 Ab	Qualitative immunoprecipitation
SAE1 (SUMO activating enzyme) Ab	Qualitative immunoblot
TIF-1 gamma (155 kDa) Ab	Qualitative immunoblot
Polymyositis Abs^c
Antibody	Method
EJ (glycyl-tRNA synthetase) Ab	Qualitative immunoprecipitation
Jo-1 (histidyl-tRNA synthetase) Ab, IgG	Semiquantitative multiplex bead assay
OJ (isoleucyl tRNA synthetase) Ab	Qualitative immunoprecipitation
PL-7 (threonyl-tRNA synthetase) Ab	Qualitative immunoprecipitation
PL-12 (alanyl-tRNA synthetase) Ab	Qualitative immunoprecipitation
SRP (signal recognition particle) Ab	Qualitative immunoprecipitation
^aThis subset of antibodies is also available as a combined dermatomyositis and myositis panel. ^bThis subset of antibodies is also available as a dermatomyositis panel. ^cThis subset of antibodies is also available as a polymyositis panel. Ab, antibody; ENA, extractable nuclear antigen; IgG, immunoglobulin G; RNP, ribonucleoprotein

Some antibodies may be orderable separately; refer to the ARUP Lab Test Directory.

Test Interpretation

Results

Positive: Antibody detected.
- Supports a clinical diagnosis of dermatomyositis, polymyositis, necrotizing autoimmune myopathy, and/or an overlap syndrome.
- Results for specific antibodies may be reported as low/weak positive, positive, or high/strong positive. Additional interpretive information for positive antibodies may be provided on the Patient Report.
- Myositis-specific antibodies are generally regarded as mutually exclusive with rare exceptions; the occurrence of two or more myositis-specific antibodies should be carefully evaluated in the context of the patient’s clinical presentation.
- Myositis-associated antibodies may be found in patients with overlap syndromes and other conditions, and are generally not specific for myositis.
Negative: Antibody not detected.

Limitations

Results are not diagnostic in the absence of other findings, and should be considered in the complete clinical context.

Negative results do not rule out a diagnosis of inflammatory myopathy or overlap syndrome.

References

30129477

Selva-O'Callaghan A, Pinal-Fernandez I, Trallero-Araguás E, et al. Classification and management of adult inflammatory myopathies. Lancet Neurol. 2018;17(9):816-828.

29865091

Schmidt J. Current classification and management of inflammatory myopathies. J Neuromuscul Dis. 2018;5(2):109-129.

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