Abstract | OBJECTIVE: 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.
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Authors | Rohit Aggarwal, Chester V Oddis, Danielle Goudeau, Noreen Fertig, Ilinca Metes, Chad Stephens, Zengbiao Qi, Diane Koontz, Marc C Levesque |
Journal | Rheumatology (Oxford, England)
(Rheumatology (Oxford))
Vol. 54
Issue 7
Pg. 1194-9
(Jul 2015)
ISSN: 1462-0332 [Electronic] England |
PMID | 25524922
(Publication Type: Evaluation Study, Journal Article, Research Support, N.I.H., Extramural, Validation Study)
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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
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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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