Aggarwal Rohit, Oddis Chester V, Goudeau Danielle, Fertig Noreen, Metes Ilinca, Stephens Chad, Qi Zengbiao, Koontz Diane, Levesque Marc C
Department of Medicine, Division of Rheumatology and Clinical Immunology, University of Pittsburgh, Pittsburgh, PA, USA
Department of Medicine, Division of Rheumatology and Clinical Immunology, University of Pittsburgh, Pittsburgh, PA, USA.
Rheumatology (Oxford). 2015 Jul;54(7):1194-9. doi: 10.1093/rheumatology/keu436. Epub 2014 Dec 17.
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.
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.
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.
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.
本研究旨在开发并验证一种用于检测肌炎患者血清中抗信号识别颗粒（SRP）自身抗体的定量酶联免疫吸附测定（ELISA），并纵向分析其与肌炎疾病活动度的相关性。
我们开发了一种血清ELISA，使用包被在ELISA板上的重组纯化全长人SRP以及结合人IgG的二抗来检测抗SRP的结合情况。蛋白质免疫沉淀法被用作检测抗SRP存在的金标准。分析了三组血清样本：经免疫沉淀法检测为SRP（+）的肌炎患者、经免疫沉淀法检测为SRP（-）的肌炎患者以及非肌炎对照。评估了ELISA的敏感性、特异性、阳性预测值和阴性预测值。评估了百分比一致性和重测信度。还检测了7名SRP免疫沉淀阳性受试者的系列样本，以及血清肌肉酶和徒手肌力测试。
通过免疫沉淀法，我们鉴定出26例SRP（+）肌炎患者和77例SRP（-）对照（包括38例坏死性肌病患者）。非肌炎对照患者包括系统性红斑狼疮（SLE，n = 4）和系统性硬化症（SSc，n = 7）患者。ELISA检测的抗SRP阳性结果与免疫沉淀法显示出高度一致性（97.1%）（κ = 0.94）。抗SRP ELISA的敏感性、特异性、阳性预测值和阴性预测值分别为88、100、100和96。曲线下面积为0.94，重测信度较强（r = 0.91，P < 0.001）。系列样本显示抗SRP水平与肌肉酶和徒手肌力测试的变化平行。
我们开发了一种用于检测血清抗SRP自身抗体的定量ELISA，并在肌炎中验证了该检测方法。通过ELISA对SRP水平进行纵向评估可能是一种有用的疾病活动生物标志物。
