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Correspondence response
Response to: ‘Comment on: standardisation of myositis-specific antibodies: where are we today?’ by Infantino et al
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  1. Johan Rönnelid1,
  2. Fabricio Espinosa-Ortega2,
  3. Ingrid E Lundberg2,3
  1. 1 Department Immunology, Genetics and Pathology, Uppsala University, Uppsala, Sweden
  2. 2 Medicine, Division of Rheumatology, Karolinska Institutet, Karolinska University Hospital, Stockholm, Sweden
  3. 3 Center for Molecular Medicine, Karolinska Institutet, Stockholm, Sweden
  1. Correspondence to Professor Ingrid E Lundberg, Medicine, Division of Rheumatology, Karolinska Institutet, Karolinska Univeristy Hospital, Stockholm SE-171 76, Sweden; ingrid.lundberg{at}ki.se

https://doi.org/10.1136/annrheumdis-2019-216248

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    We agree with the notions made by Infantino et al 1 in their reply to our previously published report2 concerning the need for multicentre studies to obtain large enough number to validate new methods for detection of myositis-specific antibodies (MSA) and myositis-associated autoantibodies (MAA). We also agree with the suggestion to evaluate the possibility to individualise reference ranges (cut-off values) for the individual autoantibodies in multi-autoantibody assays like line immune assays (LIA). In relation to such proposals, we would like to stress our experience that the same LIA might yield very quantitatively divergent results in different laboratories, for example, due to differences in laboratory temperature3 but certainly also other factors, and that these quantitative differences may result in qualitatively divergent results. One way to help standardisation of laboratory results might be to include quantitative internal controls for the individual autoantibodies included in the LIAs, as we have discussed before.4 Multicentre studies on the evaluation of LIAs or other methods for detection of MSA and MAA should preferably be combined with use of such common internal controls in the participating laboratories.

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    References

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      2. Infantino M ,
      3. Manfredi M ,
      4. Bizzarro N
      . Comment on: standardisation of myositis-specific antibodies: where are we today? Ann Rheum Dis 2021;80:e115.
    2. ↵
      2. Espinosa-Ortega F ,
      3. Holmqvist M ,
      4. Alexanderson H , et al
      . Comparison of autoantibody specificities tested by a line blot assay and immunoprecipitation-based algorithm in patients with idiopathic inflammatory myopathies. Ann Rheum Dis 2019;78:858–60.doi:10.1136/annrheumdis-2018-214690
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    3. ↵
      2. Rönnelid J ,
      3. Barbasso Helmers S ,
      4. Storfors H , et al
      . Use of a commercial line blot assay as a screening test for autoantibodies in inflammatory myopathies. Autoimmun Rev 2009;9:58–61.doi:10.1016/j.autrev.2009.03.005
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    4. ↵
      2. Rönnelid J ,
      3. Espinosa-Ortega F ,
      4. Lundberg IE
      . Response to: ‘Semi-quantitative analysis of line blot assay for myositis-specific and myositis-associated antibodies: a better performance?’ by Cavazzana et al. Ann Rheum Dis 2020;79:e153. doi:10.1136/annrheumdis-2019-215967

    Footnotes

    • Handling editor Josef S Smolen

    • Twitter @fabstag

    • Contributors All authors have equally contributed.

    • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

    • Competing interests None declared.

    • Provenance and peer review Commissioned; internally peer reviewed.

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