Significance Of Anti-SMD1 Antibody In Diagnosis Of Systemic Lupus Erythematosus

Objective: Systemic lupus eythematosus is a type of autoimmune disease with multisystemic impairments and multi-autoantibodies. Due to its complicated clinical manifestations, it is difficult to diagnose merely by depending the clinical manifestations and examination of autoantibody is needed. Up to now, the laboratory examinations of SLE mainly include anti-dsDNA antibody, anti-Sm antibody and anti-AnuA antibody etc. The former two are the specificity indexes of SLE, however, the current rates of successful detection for those two are both low: only between 5% to 30%. Therefore, it is a challenge for the field of laboratory diagnosis of rheumatism to find new diagnose markers of SLE with high sensitivity and strong specificity. The anti-Sm antibody is compound which is constituted by a group of glucoproteins and small nuclear ribonucleoproteins, and it is generally recognized as an important evidence to the diagnosis of SLE and an indicating antibody of SLE. Nevertheless, a severe deficiency of the anti-Sm antibody is that the masculine rate in SLE is only 30% approximately so that it is apt to result in wrong diagnosis. According to the study literature, the anti-Sm antibody is compounded with multi-protein including U-RNA, B', B, N, D1, D2, D3, E, F and G etc, where D1 is the major antigen. It can greatly improve the detection rate of anti-Sm antibody by substituting the whole anti-Sm antibody with Sm D1 amino acid sequence (aa83-119) as the antigen. In this study, 48 cases of SLE patients were chosen and their levels of anti-SmD1 antibody were detected by quantitative ELISA assay, anti-dsDNA and anti-Sm antibodies were detected by indirect immunofluorescence as well as anti-nuclear antibody (ANA) by immunofluorescence analysis. At the meantime, comparison work was also conducted between the serum of 20 cases of patients with other connective tissue diseases and and the serum of 20 cases of healthy people. The purpose of this study is to evaluate the sensitivity and specificity of the anti-SmD1 antibody in the diagnosis of SLE as well as it relationships with clinical manifestations and reactiveness.Methods:1 88 serum samples were chosen and they were divided into three groups: (1) systemic lupus erythematosus group (Group A), i.e. 48 cases of SLE patients; (2) other connective tissue disease group (Group B), i.e. 20 cases of other connective tissue diseases Patients (such as rheumatoid arthritis, scleroderma, dermatomyositis and dryness syndrome etc); (3) healthy control group (Group C), 20 samples by selecting randomly from healthy volunteers.2 In this study, the level of anti-SmD1 antibody were detected by quantitative ELISA assay, anti-dsDNA and anti-Sm antibodies were detected by indirect immunofluorescence as well as anti-nuclear antibody (ANA) by immunofluorescence analysis. During this period, the clinical manifestations (including fever, emerging rash, arthritis, hair loss, mouth ulcers, central nervous system damage) were recorded, also, the laboratory exmination results (including blood, urine, stool examination, alexine, antinuclear antibody, anti-dsDNA antibody, anti-Sm antibody, anti-SmD1 antibody, echocardiography, abdominal ultrasonography, lung CT) and the disease activity points were included, and so on.3 Statistical analysis of data: The data presented as X±S. The measurement data were analyzed with rank-sum test. The enumeration data were analyzed with chi-square test. The correlation between variables were analyzed with spearman correlation analysis. Taking P <0.05 as the range of significant difference.Results:1 The sensitivities of anti-SmD1 antibody, anti-Sm antibodies, anti-dsDNA antibody, anti-ANA antibodies in the diagnosis of systemic lupus erythematosus were 64.6%, 18.7%, 41.6%, 95.8%, respectively; specificitise were 95%, 100%, 100%, 75%. Both the sensitivity and the specificity of Anti-SmD1 antibodies were high. 2 The sensitivity of anti-SmD1 antibody and anti-dsDNA antibody jointed detection for the diagnosis of SLE was 79.1% and the specificity was 95%.3 The anti-SmD1 antibodies had significant relationships with the kidney damage, fever, rash, pleurisy, and didn't have obvious relationships with the white blood cells, platelets, antinuclear antibody, alexine, mouth ulcer, central nervous system damage, haematuria, baldness.4 The serum level of anti-SmD1 antibodies and systemic lupus erythematosus disease activity index were positively correlated (P <0.05).5 The SLEDAI of SLE patients with positive anti-dsDNA were significantly higher than that of anti-dsDNA-negative patients (P <0.05).6 There was no significant difference between the SLEDAI of anti-Sm- positive Systemic lupus erythematosus and the SLEDAI of anti-Sm-negative Systemic lupus erythematosus (P> 0.05).7 There was no significant difference between the SLEDAI of anti-ANA- positive Systemic lupus erythematosus and the SLEDAI of anti-ANA-negative Systemic lupus erythematosus (P> 0.05).Conclusions:1 Anti-SmD1 antibody has high sensitivity and specificity of diagnosis of SLE and it can be used as a reference indicator.2 The combined detection of anti-dsDNA antibodies and anti-SmD1 antibo- dies can increase the sensitivity of SLE diagnosis.3 The anti-SmD1 antibodies had significant relationships with the kidney damage, fever, rash, pleurisy and didn't have obvious relationships with the white blood cells, platelets, antinuclear antibody, alexine, mouth ulcer, central nervous system damage, haematuria, baldness. The results could provide some basis for further study of the pathogenesis of SLE.4 The quantitation of anti-SmD1 antibody was positively correlated with SLEDAI and it could provid a certain reference value for the determine of activity.5 The quantitation of anti-dsDNA antibody was positively correlated with SLEDAI and it could provid a certain reference value for the determine of activity.6 There were no significant relationships between anti-Sm antibody or anti-nuclear antibody and the activity of SLE.