title: False decrease of HBsAg S/CO values in serum with high-concentration rheumatoid factors.
abstract: OBJECTIVE
  To investigate whether high-concentration RFs cause false decrease of S/CO values of serum HBsAg.
  
  
  METHODS
  Serum HBsAg was determined in 100 RF-positive sera using one-step ELISA. Twenty-three HBsAg-negative sera with high-concentration RFs were selected randomly to perform dilution with mixed normal sera. Serum models consisting of HBsAg and high-concentration RFs were made by blending high-concentration RFs and HBsAg-positive sera at the ratio of 9:1.
  
  
  RESULTS
  In the 23 samples, one-step ELISA showed that HBsAg-positive rate was 69.57% at dilution of 1:2, 60.87% at dilution of 1:4 and 40.00% at dilution of 1:8, whereas two-step ELISA showed that it was 100% without any dilution. Thirty serum models were made and divided into six groups. Median S/CO value of HBsAg was 3.00 in control, whereas it ranged from 0.13 to 1.78 in the six groups.
  
  
  CONCLUSIONS
  High-concentration RFs cause false decrease of S/CO values of HBsAg using one-step ELISA.
authors.affiliation: Laboratory Department, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022, China.
authors.forename: Lei
authors.initials: L
authors.lastname: Xu
authors.forename: Xueping
authors.initials: X
authors.lastname: Wang
authors.forename: Ronghong
authors.initials: R
authors.lastname: Ma
authors.forename: Xiaoqian
authors.initials: X
authors.lastname: Zeng
authors.forename: Bing
authors.initials: B
authors.lastname: Wu
authors.forename: Lihua
authors.initials: L
authors.lastname: Hu
authors.forename: Yirong
authors.initials: Y
authors.lastname: Li
mesh_terms: D000327:Adsorption; D001172:Arthritis, Rheumatoid / Q000097:blood; D001774:Blood Chemical Analysis; D004797:Enzyme-Linked Immunosorbent Assay; D005189:False Positive Reactions; D006514:Hepatitis B Surface Antigens / Q000097:blood*; D019694:Hepatitis B, Chronic / Q000097:blood* / Q000175:diagnosis; D006801:Humans; D012217:Rheumatoid Factor / Q000097:blood* / Q000302:isolation & purification
chemical_list: D006514:Hepatitis B Surface Antigens; D012217:Rheumatoid Factor