title: [Detection of anti-SSA/Ro antibody by ELISA, double immunodiffusion, and immunoblotting: a comparative study].
abstract: OBJECTIVE
  To compare the specificity and sensitivity of ELISA, double immunodiffusion (ID), and immunoblotting (IB) in detection of anti-SSA/Ro antibodies in the sera of patients with connective tissue disease (CTD).
  
  
  METHODS
  ELISA, double ID, and IB were used to detect the serum levels of anti-SSA/Ro antibodies in 7736 patients undergoing screening of CTD, 122 healthy blood donors, and 166 CTD patients positive in antinuclear antibody (ANA) and/or anti-extractable nuclear antigen (ENA).
  
  
  RESULTS
  (1) The sera of the 122 healthy blood donors were all negative in anti-SSA/Ro antibodies by these three methods. (2) 1085 of the 7736 sera undergoing screening of CTD were positive in the anti-SSA/R0 antibody of the relative molecular quantity of 52,000. Ninety-two of the 1085 patient, ANA and/or anti-ENA negative, were all confirmed by ELISA and ID to be negative in anti-SSA/R0 antibodies. And 993 of these 1085 patients were positive in ANA and/or anti-ENA antibody, 917 of which were shown to be anti-SSA/R0 antibodies positive by ELISA (92.3%, 917/993), and 860 of which were shown to be anti-SSA/R0 antibodies positive by ID (86.6%, 860/993). (3) The prevalence rates of anti-SSA/Ro antibodies in the 166 CTD patients detected by ELISA, ID, and IB respectively were 76.5% (127/166), 65.1% (108/166), and 49.4% (82/166) respectively. (4) 127 of the 166 sera of the CTD group were anti-SSA/Ro antibody positive By ELISA, and 108 of the 166 sera were anti-SSA/R0 antibody positive by ID, with a coincidence rate of ELISA and ID of 88.6% (147/166), and there was a significant difference in positive rate of anti-SSA/Ro antibody between these two methods (P < 0.001). 81 of the 166 CTD sera were anti-SSA/Ro antibody positive with a positive rate of 63.8%. The coincidence rate of ID and IB was 75.9% (126/166) and there was a significant difference in positive rate of anti-SSA/Ro antibody between ID and IB methods too (P < 0.001). (5) Spearman's rank correlation study showed that the correlation coefficient between ELISA and ID was 0.828 (P < 0.001).
  
  
  CONCLUSIONS
  (1) ELISA and ID are more specific than IB in detection of anti-SSA/Ro antibody. (2) The specificity of IB was lower, however, when ANA and/or other anti-ENA are positive, its specificity would be improved markedly. (3) ELISA is more sensitive than ID, and ID is more sensitive than IB in detection of anti-SSA/Ro antibody. (4) There is a significant positive correlation between ELISA and ID quantitatively.
authors.affiliation: Department of Rheumatology, Peking Union Medical College Hospital, Peking Union Medical College and Chinese Academy of Medical Sciences. Beijing, China.
authors.forename: Sheng-quan
authors.initials: SQ
authors.lastname: Tong
authors.forename: Qun
authors.initials: Q
authors.lastname: Shi
authors.forename: Xiao-hong
authors.initials: XH
authors.lastname: Wen
authors.forename: Xiao-dan
authors.initials: XD
authors.lastname: Gan
authors.forename: Yan-ping
authors.initials: YP
authors.lastname: Shi
authors.forename: Yan
authors.initials: Y
authors.lastname: Zhao
authors.forename: Xiao-feng
authors.initials: XF
authors.lastname: Zeng
authors.forename: Feng-chun
authors.initials: FC
authors.lastname: Zhang
authors.forename: Yi
authors.initials: Y
authors.lastname: Dong
mesh_terms: D000974:Antibodies, Antinuclear / Q000097:blood*; D003240:Connective Tissue Diseases / Q000097:blood* / Q000175:diagnosis; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods; D006801:Humans; D015151:Immunoblotting / Q000379:methods; D005779:Immunodiffusion / Q000379:methods; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
chemical_list: D000974:Antibodies, Antinuclear; C035356:SS-A antibodies