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FeedbackSemi-Quantitative Enzyme-Linked Immunosorbent Assay (ELISA) / Qualitative Immunoprecipitation / Semi-Quantitative Multiplex Bead Assay / Qualitative Immunoblot / Semi-Quantitative Indirect Fluorescent Antibody (IFA) / Qualitative Particle-Based Multianalyte Technology (PMAT)
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 as overlap syndromes with connective tissue diseases. , 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, i.e., the panel that most closely matches the patient’s complete clinical phenotype, is recommended.
| ARUP Panel to Consider | Clinical Utility | Additional Test Information |
|---|---|---|
Dermatomyositis and Polymyositis Panel 3018866 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 | Dermatomyositis and Polymyositis Panel Test Fact Sheet |
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 | Polymyositis Panel Test Fact Sheet |
Dermatomyositis Autoantibody Panel 3018870 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 | Dermatomyositis Autoantibody Panel Test Fact Sheet |
Interstitial Lung Disease Autoantibody Panel 3018869 Antibodies overlap with the antibodies on this panel | May be useful for the evaluation of patients with interstitial lung disease with or without other signs and symptoms of myositis | Interstitial Lung Disease Autoantibody Panel Test Fact Sheet |
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.
| Myositis-Specific Antibodiesa | |
| Dermatomyositis-Specific Antibodiesb,c | |
| Antibody | Method |
MDA5 (CADM-140) Ab | Qualitative PMAT |
| Mi-2 (nuclear helicase protein) Ab | Qualitative immunoprecipitation |
| NXP2 (nuclear matrix protein-2) Ab | Qualitative PMAT |
| P155/140 Ab | Qualitative immunoprecipitation |
| SAE1 (SUMO activating enzyme) Ab | Qualitative PMAT |
| TIF-1 gamma (155 kDa) Ab | Qualitative PMAT |
| Antisynthetase Syndrome-Specific Antibodiesb,d | |
| Antibody | Method |
| EJ (glycyl-tRNA synthetase) Ab | Qualitative immunoprecipitation |
| Ha (tyrosyl-tRNA synthetase) Ab | Qualitative immunoblot and qualitative immunoprecipitation |
| Ks (asparaginyl-tRNA synthetase) Ab | Qualitative immunoblot and 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 |
| Zo (phenylalanyl-tRNA synthetase) Ab | Qualitative immunoblot and qualitative immunoprecipitation |
| Necrotizing Myopathy-Specific Antibodies | |
| Antibody | Method |
| HMGCR (3-hydroxy-3-methylglutaryl-coenzyme A reductase) Ab, IgG | Qualitative PMAT; if positive, reflex to semi-quantitative ELISA |
| SRP (signal recognition particle) Abb,d | Qualitative immunoprecipitation |
| Myositis-Associated Antibodiese | |
| Antibody | Method |
| Antinuclear Ab (ANA), Hep-2, IgGf | Semiquantitative indirect fluorescent antibody |
| Fibrillarin (U3 RNP) Ab, IgG | Qualitative immunoblot |
| Ku Ab | Qualitative immunoprecipitation |
| PM/Scl-100 Ab, IgG | Qualitative immunoblot |
| Smith/RNP (ENA) Ab, IgG | Semiquantitative ELISA |
| SSA-52 (Ro52) (ENA) Ab, IgG | Semiquantitative multiplex bead assay |
| SSA-60 (Ro60) (ENA) Ab, IgG | Semiquantitative multiplex bead assay |
aMyositis-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. Refer to the ARUP Consult Inflammatory Myopathies – Myositis topic for more information about myositis. bThis subset of antibodies is also available as a combined dermatomyositis and polymyositis panel cThis subset of antibodies is also available as a dermatomyositis panel. dThis subset of antibodies is also available as a polymyositis panel. eMyositis-associated antibodies may be found in patients with overlap syndromes and other conditions and are generally not specific for myositis. fThe presence of ANA is a feature of systemic autoimmune rheumatic diseases, however, ANA lacks diagnostic specificity and may occur in the general population. Positive ANA must be confirmed by more specific serologic tests. For more information, refer to the Antinuclear Antibody (ANA) With Hep-2 Substrate Test Fact Sheet. Ab, antibody; ELISA, enzyme-linked immunosorbent assay; ENA, extractable nuclear antigen; IgG, immunoglobulin G; PMAT, particle-based multianalyte technology; RNP, ribonucleoprotein | |
Some antibodies may be orderable separately; refer to the ARUP Laboratory 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.
- Antinuclear antibody (ANA) results are reported as a pattern and titer. For more information on the interpretation of ANA results, refer to the Antinuclear Antibody (ANA) With Hep-2 Substrate Test Fact Sheet.
- 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
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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.
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29865091
Schmidt J. Current classification and management of inflammatory myopathies. J Neuromuscul Dis. 2018;5(2):109-129.