title: Negative interference in serum HBsAg ELISA from rheumatoid factors.
abstract: BACKGROUND
  RF(Rheumatoid factor) is usually thought to cause positive interference in immunoassay. Recently, our study showed that high-concentration RFs caused negative interference as well as positive interference in serum HBsAg(Hepatitis B surface antigen) ELISA(Enzyme-linked immunosorbent assay), but it is unclear that RF causing negative interference is an anomaly produced by a certain ELISA kit or a common property of most of HBsAg ELISA kits.
  
  
  METHODS
  Serum models were made by blending HBsAg-positive sera and high- or moderate-concentration RFs sera at the ratio of 1: 9, then one-step and two-step ELISA were adopted to determine HBsAg in serum models.
  
  
  RESULTS
  No matter what kind of kit used, one-step ELISA showed that HBsAg S/CO( sample/cut off) values in serum models were significantly lower than original values. Bivariate correlations tests showed decline rates of HBsAg S/CO Values were not associated to serum RF concentrations ranging from 288 to 3560 IU/mL. HBsAg converted to be negative in 69.80% serum models with original-value ranging from 1.00 to 10.00, and in 2.68% serum models with higher original-value. RF causing decline of HBsAg S/CO value provided by one-step ELISA was more obvious than that provided by two-step ELISA.
  
  
  CONCLUSIONS
  It is concluded that susceptibility of all HBsAg ELISA assays to interference from RF, leading to predominantly lower and in some cases "false-negative" results, and moreover, the lower the original HBsAg S/CO Value, the higher the false-negative rate.
authors.affiliation: Department of Laboratory Medicine , Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.
authors.forename: Lei
authors.initials: L
authors.lastname: Xu
authors.forename: Zhen
authors.initials: Z
authors.lastname: Yu
authors.forename: Wen
authors.initials: W
authors.lastname: Fan
authors.forename: Xueping
authors.initials: X
authors.lastname: Wang
authors.forename: Mingshui
authors.initials: M
authors.lastname: Xie
authors.forename: Yiting
authors.initials: Y
authors.lastname: Xu
authors.forename: Lihua
authors.initials: L
authors.lastname: Hu
authors.forename: Yirong
authors.initials: Y
authors.lastname: Li
mesh_terms: D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods / Q000592:standards*; D006509:Hepatitis B / Q000175:diagnosis / Q000276:immunology; D006514:Hepatitis B Surface Antigens / Q000097:blood* / Q000276:immunology; D006515:Hepatitis B virus / Q000276:immunology; D006801:Humans; D011933:Reagent Kits, Diagnostic; D012217:Rheumatoid Factor / Q000097:blood* / Q000276:immunology; D012680:Sensitivity and Specificity
chemical_list: D006514:Hepatitis B Surface Antigens; D011933:Reagent Kits, Diagnostic; D012217:Rheumatoid Factor