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Anti-signal recognition particle autoantibody ELISA validation and clinical associations.

AbstractOBJECTIVE:
The aim of this study was to develop and validate a quantitative anti-signal recognition particle (SRP) autoantibody serum ELISA in patients with myositis and longitudinal association with myositis disease activity.
METHODS:
We developed a serum ELISA using recombinant purified full-length human SRP coated on ELISA plates and a secondary antibody that bound human IgG to detect anti-SRP binding. Protein immunoprecipitation was used as the gold standard for the presence of anti-SRP. Serum samples from three groups were analysed: SRP(+) myositis subjects by immunoprecipitation, SRP(-) myositis subjects by immunoprecipitation and non-myositis controls. The ELISA's sensitivity, specificity, positive predictive value and negative predictive value were evaluated. Percentage agreement and test-retest reliability were assessed. Serial samples from seven SRP immunoprecipitation-positive subjects were also tested, along with serum muscle enzymes and manual muscle testing.
RESULTS:
Using immunoprecipitation, we identified 26 SRP(+) myositis patients and 77 SRP(-) controls (including 38 patients with necrotizing myopathy). Non-myositis control patients included SLE (n = 4) and SSc (n = 7) patients. Anti-SRP positivity by ELISA showed strong agreement (97.1%) with immunoprecipitation (κ = 0.94). The sensitivity, specificity, positive predictive value, and negative predictive value of the anti-SRP ELISA were 88, 100, 100 and 96, respectively. The area under the curve was 0.94, and test-retest reliability was strong (r = 0.91, P < 0.001). Serial samples showed that anti-SRP levels paralleled changes in muscle enzymes and manual muscle testing.
CONCLUSION:
We developed a quantitative ELISA for detecting serum anti-SRP autoantibodies and validated the assay in myositis. Longitudinal assessment of SRP levels by ELISA may be a useful biomarker for disease activity.
AuthorsRohit Aggarwal, Chester V Oddis, Danielle Goudeau, Noreen Fertig, Ilinca Metes, Chad Stephens, Zengbiao Qi, Diane Koontz, Marc C Levesque
JournalRheumatology (Oxford, England) (Rheumatology (Oxford)) Vol. 54 Issue 7 Pg. 1194-9 (Jul 2015) ISSN: 1462-0332 [Electronic] England
PMID25524922 (Publication Type: Evaluation Study, Journal Article, Research Support, N.I.H., Extramural, Validation Study)
Copyright© The Author 2014. Published by Oxford University Press on behalf of the British Society for Rheumatology. All rights reserved. For Permissions, please email: [email protected].
Chemical References
  • Autoantibodies
  • Biomarkers
  • Signal Recognition Particle
Topics
  • Adult
  • Autoantibodies (blood)
  • Biomarkers (blood)
  • Case-Control Studies
  • Enzyme-Linked Immunosorbent Assay (methods)
  • Female
  • Humans
  • Male
  • Middle Aged
  • Muscle, Skeletal (enzymology)
  • Myositis (blood, diagnosis, immunology)
  • Predictive Value of Tests
  • Reproducibility of Results
  • Sensitivity and Specificity
  • Severity of Illness Index
  • Signal Recognition Particle (immunology)
  • Time Factors

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