A Commercial Anti-TIF1γ ELISA Is Superior to Line and Dot Blot and Should Be Considered as Part of Routine Myositis-Specific Antibody Testing

Newer Autoantibodies and Laboratory Assessments in Myositis

PURPOSE OF REVIEW

We aim to describe the immunoassays that have been used for myositis autoantibody discovery with a focus on newer methods. We describe recently identified myositis autoantibodies that do not yet form part of routine clinical testing, highlighting what is known about their associated clinical phenotype and potential clues as to their presence.

RECENT FINDINGS

Novel approaches to autoantibody detection have been employed in recent years including chemiluminescent immunoassay, phage immunoprecipitation-sequencing and modifications to the more traditional immunoprecipitation technique. This has led to the discovery of novel autoantibodies, including novel anti-aminoacyl-tRNA synthetase autoantibodies and autoantibodies which modify cancer risk for patients with anti-TIF1ɣ associated dermatomyositis. New approaches to novel autoantibody detection have facilitated autoantibody discovery and will enable the identification of autoantibodies to a broader range of autoantigens. Challenges remain in translating this knowledge into accessible testing particularly given the rarity of most recently discovered autoantibodies.

Autoantibody testing in myositis: an update

PURPOSE OF REVIEW

This review aims to provide an update on myositis autoantibody testing strategies. We have focussed on the reliability and usefulness of different myositis autoantibody detection methods, including commonly used solid phase immunoassays and newer discovery techniques.

RECENT FINDINGS

Several studies have highlighted the limitations of currently available immunoassays, particularly when used in populations with low pretest probability and without supporting clinical evidence. While many autoantibodies, such as anti-Jo1, are detected with high sensitivity and specificity, the low incidence of myositis autoantibodies in tested populations reduces their positive predictive value. The low sensitivity of line immunoassays to detect key myositis autoantibodies, including anti-TIF1γ and rarer antisynthetase autoantibodies, is a concern.

SUMMARY

Myositis autoantibodies are widely accepted as important clinical tools, and hence, there is a significant demand for reliable, accessible, and affordable detection methods. False positives and negative results have the potential to impact on patient care, particularly for malignancy and lung disease associated autoantibodies. Increased availability of myositis autoantibody testing has led to a rise in requests from a broader range of clinicians. It is critically important that clinicians are aware of specific limitations of tests and interpret results in the context of clinical findings.

Assessing the sensitivity and specificity of myositis-specific and associated autoantibodies: a sub-study from the MyoCite cohort

OBJECTIVES

Myositis-specific and associated autoantibodies are important biomarkers in routine clinical use. We assessed local testing performance for myositis autoantibodies by comparing line immunoassay (LIA) to protein radio-immunoprecipitation and identifying clinical characteristics associated with each myositis autoantibody in the MyoCite cohort.

METHODS

Serum samples from patients within the MyoCite cohort, a well-characterized retro-prospective dataset of adult and juvenile idiopathic inflammatory myopathy (IIM) patients in Lucknow, India (2017-2020), underwent LIA at Sanjay Gandhi Postgraduate Institute of Medical Science (SGPGIMS), Lucknow. Immunoprecipitation of 147 IIM patients' serum samples (125 adult-onset, 22 juvenile-onset) was conducted at the University of Bath, with researchers blind to LIA results. LIA performance was assessed against immunoprecipitation as the reference standard, measuring sensitivity, specificity and inter-rater agreement. Univariate and multivariate logistic regression determined clinical associations for specific myositis-specific autoantibodies.

RESULTS

Immunoprecipitation identified myositis autoantibodies in 56.5% (n = 83) of patient samples, with anti-Jo1 (n = 16; 10.9%) as the most common, followed by anti-MDA5 (n = 14, 9.5%). While LIA showed good agreement for anti-Jo1, anti-PL7 and anti-PL12 (Cohen's κ 0.79, 0.83 and 1, respectively), poor agreement was observed in other subgroups, notably anti-TIF1γ (Cohen's κ 0.21). Strongly positive samples, especially in myositis-specific autoantibodies, correlated more with immunoprecipitation results. Overall, 59 (40.1%) samples exhibited non-congruence on LIA and immunoprecipitation, and κ values for LIAs for anti-TIF1γ, anti-Ku, anti-PmScl, anti-Mi2 and anti-SAE ranged between 0.21 and 0.60.

CONCLUSION

While LIA reliably detected anti-Jo1, anti-PL7, anti-PL12, anti-MDA5 and anti-NXP-2, it also displayed false positives and negatives. Its effectiveness in detecting other autoantibodies, such as anti-TIF1γ, was poor.

Dermatomyositis: Practical Guidance and Unmet Needs

Dermatomyositis is a heterogeneous idiopathic inflammatory myopathy associated with various cutaneous manifestations and variable presence of myositis, interstitial lung disease, and other visceral organ involvement. An accurate diagnosis of dermatomyositis requires correlating clinical examination findings with serological and histological findings. Familiarity with pathognomonic and common cutaneous manifestations of dermatomyositis, which are highlighted here, can be especially helpful in making an accurate diagnosis. Additionally, evaluating patients for presence of myositis-specific autoantibodies can further support or refute a dermatomyositis diagnosis. When present, myositis-specific autoantibodies can also help guide workups for various dermatomyositis-associated manifestations, as each is associated with relatively distinct clinical characteristics. Evaluating patients for various systemic manifestations often relies on expert opinion recommendations; however, societal guideline statements concerning the evaluation of some manifestations have recently been described. Although malignancy-associated dermatomyositis is a well-accepted subtype, there is limited evidence to support extensive malignancy screening has a favorable benefit-risk ratio in most dermatomyositis patients. However, recent research has uncovered novel associations between dermatomyositis and malignancy, suggesting the possibility of identifying high-risk subsets of dermatomyositis patients in whom malignancy screening may have a high value. Treatment for dermatomyositis has remained largely unchanged over the past several decades. Although many dermatomyositis patients can be effectively treated with current options, either as monotherapy or with combination regimens, there is a need for more targeted and effective DM therapies, in general, and for MDA5(+) dermatomyositis-associated rapidly progressive interstitial lung disease. Fortunately, significant current and emerging research activities evaluating various novel medications for dermatomyositis provide hope for exciting future advances in patients with this intriguing immune-mediated disease.

Polymyositis and dermatomyositis biomarkers

Polymyositis (PM) and dermatomyositis (DM) are the two subtypes of idiopathic inflammatory myositis and are characterized as symmetrical progressive muscle weakness in the proximal extremities. PM/DM affect multiple organs and systems, including the cardiovascular, respiratory and digestive tract systems. An in-depth understanding of PM/DM biomarkers will facilitate development of simple and accurate strategies for diagnosis, treatment, and prognosis prediction. This review summarized the classic biomarkers of PM/DM, including anti-aminoacyl tRNA synthetases (ARS) antibody, anti-Mi-2 antibody, anti-melanoma differentiation-associated gene 5 (MDA5) antibody, anti-transcription intermediary factor 1-γ (TIF1-γ) antibody, anti-nuclear matrix protein 2 (NXP2) antibody, among others. Among them, anti-aminoacyl tRNA synthetases antibody is the most classic. In addition, many potential novel biomarkers were also discussed in this review, including anti-HSC70 antibody, YKL-40, interferons, myxovirus resistance protein 2, regenerating islet-derived protein 3-α, interleukin (IL)-17, IL-35, microRNA (miR)-1 and so on. Among the biomarkers of PM/DM described in this review, classic biomarkers have become the mainstream biomarkers to assist clinicians in diagnosis due to their early discovery, in-depth research, and widespread application. The novel biomarkers also have potential and broad research prospects, which will make immeasurable contributions to exploring biomarker-based classification standards and expanding their application value.

Update on dermatomyositis

PURPOSE OF REVIEW

This review summarizes and comments on current knowledge in dermatomyositis.

RECENT FINDINGS

The 2018 European Neuromuscular Centre classification of dermatomyositis has been challenging by the discovery of clinicopathological features associated with dermatomyositis-specific antibody (DMSA) that were not incorporated in the original criteria. These features include but may not be limited to the presence of perifascicular necrosis in anti-Mi-2 dermatomyositis; presence of diffuse nonperifascicular sarcoplasmic myxovirus resistance protein A expression in anti-MDA5 dermatomyositis; and dermatomyositis sine dermatitis in anti-NXP-2 dermatomyositis. Variations and subclassifications within the same DMSA subtypes are observed: anti-MDA5 dermatomyositis is clinically subcategorized into good, intermediate, and poor prognostic subgroups; concurrent anti-CCAR1 and anti-TIF1-γ positivity identify anti-TIF1-γ-positive patient with a lower risk for cancer-associated myositis. Owing to distinct IFN1-signaling pathway activation in dermatomyositis, JAK-STAT inhibitor - the pathway-targeted therapy, have been studied with promising results in refractory dermatomyositis and some new-onset dermatomyositis. In addition, the potential serum biomarkers for IFN1 pathway activation are being investigated for their performance in monitoring the disease activity and the efficacy of the treatment.

SUMMARY

DMSA, evidence of prominent IFN1 pathway activation, and risk/severity-associated biomarkers would likely play major roles in future dermatomyositis classification, disease monitoring, and treatment decision.

The use of ELISA is comparable to immunoprecipitation in the detection of selected myositis-specific autoantibodies in a European population

Background

The reliable detection of myositis-specific autoantibodies (MSA) provides valuable clinical information regarding prognosis, clinical progression and diagnostic confirmation.

Objectives

To evaluate the reliability of a commercial ELISA immunoassay in detecting myositis-specific autoantibodies in comparison to immunoprecipitation as the reference standard.

Methods

Serum samples were chosen from a biobank of more than 3000 samples. Samples with a confirmed MSA on Immunoprecipitation (n=116) were evaluated in duplicate by ELISA to detect Mi2, MDA5, Jo1, EJ, KS, PL-7 and PL-12 (Medical & Biological Laboratories Co. Ltd, Nagoya, Aichi, Japan). Healthy control samples (n=246) confirmed autoantibody negative by immunoprecipitation were similarly assessed.

Results

There was a very good agreement between ELISA and immunoprecipitation for serum samples containing anti-Mi2, MDA5, Jo1, EJ, KS and PL-7 and PL-12 auto-antibodies. Cohen’s κ values ranged from 0.86-1 for the measured autoantibodies on ELISA.

Conclusion

ELISA was an accurate method for detecting anti-synthetase, anti-Mi2 and anti-MDA5 autoantibodies.