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目的 探讨传染性非典型肺炎又称严重急性呼吸综合征(SARS),冠状病毒(SARS-CoV)抗体在SARS病原学诊断中的特异性及其在系统性红斑狼疮(SLE)、类风湿性关节炎(RA)、干燥综合征(SS)和混合结缔组织病(MCTD)患者中的假阳性问题。方法 应用酶联免疫吸附试验(ELISA)和荧光定量RT-PCR技术检测了111名正常对照和58例SLE、20例RA、10例SS、16例MCTD患者做血清中SARS-CoV抗体的检测。结果 在111名正常对照中,IgM抗体均阴性,IgG抗体的阳性率为3.6％;IgG抗体诊断SARS的特异性为96.4％,两种抗体同时阳性诊断SARS的特异性为100％。58例SLE患者中,IgM抗体和IgG抗体阳性率分别为8.6％和32.8％,IgG抗体和IgM抗体同时阳性为19％;在10例SS患者中只有1例两种抗体同时阳性(10％);在16例MCTD患者中,IgG抗体阳性6例(37.5％),两种抗体同时阳性1例(6.3％);在20例RA患者中只有1例IgG抗体阳性(5％)。经RT-PCR检测,上述自身免疫病患者中的阳性病例血清SARS-CoV抗体均为阴性。结论用非纯化抗原制备的ELISA试剂盒测定自身免疫病患者的SARS-CoV抗体,可能出现假阳性,两种抗体同时测定可降低诊断的假阳性率,提高诊断的特异性。在自身免疫病患者中出现假阳性的原因可能与包被的抗原有关。
Objective To investigate the specificity of SARS and coronavirus (SARS-CoV) antibodies in the etiological diagnosis of SARS and their roles in the diagnosis of systemic lupus erythematosus (SLE), rheumatoid arthritis False positive problems in patients with inflammatory (RA), Sjogren’s Syndrome (SS) and mixed connective tissue disease (MCTD). Methods Serum samples of SARS-CoV were detected by enzyme-linked immunosorbent assay (ELISA) and real-time RT-PCR in 111 normal controls and 58 patients with SLE, 20 patients with RA, 10 patients with SS and 16 patients with MCTD. Results In 111 normal controls, the IgM antibody was negative and the IgG antibody positive rate was 3.6%. The specificity of IgG antibody in diagnosing SARS was 96.4%. The specificity of the two antibodies for simultaneously diagnosing SARS was 100%. Among 58 SLE patients, the positive rates of IgM antibody and IgG antibody were 8.6% and 32.8%, respectively. The positive rates of IgG antibody and IgM antibody were 19%. Only one of the 10 patients with SS was positive (10%), In 16 MCTD patients, 6 were positive for IgG (37.5%) and 1 was positive for both (6.3%). Only 1 of the 20 RA patients was IgG positive (5%). Serum SARS-CoV antibodies were all negative in positive cases of these autoimmune diseases by RT-PCR. Conclusion The ELISA kit of non-purified antigen was used to detect SARS-CoV antibody in patients with autoimmune diseases, which may be false positive. The simultaneous determination of two antibodies can reduce the false positive rate of diagnosis and improve the diagnostic specificity. The cause of false positives in patients with autoimmune disease may be related to coated antigens.