title: Immunoglobulin G-Rheumatoid Factor Interferes Negatively with Serum Hepatitis B Envelope Antigen Chemiluminescent Microparticle Immunoassay.
abstract: BACKGROUND
  Rheumatoid factor (RF) can interfere both positively and negatively in immunoassays. It remains unclear whether the negative interference is an exceptional phenomenon or a denominator of immunoassays and which RF subgroup plays a key role in its causation.
  
  
  METHODS
  Serum models comprising hepatitis B envelope antigen (HBeAg) and RF were made by blending HBeAg-positive sera and RF-positive sera at a ratio of 1:9. Paramagnetic microparticles coated with P human chorionic gonadotropin (betaHCG)-anti-betaHCG complexes were used to remove RFs from the models, and HBeAg was determined in models using the chemiluminescent microparticle immunoassay (CMIA).
  
  
  RESULTS
  HBeAg sample/cutoff (S/CO) relative light units (RLUs) measured in 27.06% of the serum models were significantly lower than those in the control models with a maximum decline rate of > 70.00%. The discrepancies between the HBeAg S/CO RLUs measured in serum and control models were not associated with the serum RF levels when these ranged from 20 to 1510 IU/mL. Pretreatment of the serum models with the paramagnetic microparticles increased the HBeAg S/CO RLUs measured and decreased the immunoglobulin (Ig) A-RF and IgG-RF levels significantly. However, the discrepancies between the HBeAg S/CO RLUs measured in serum models before and after pretreatment were only associated inversely with the discrepancies in IgG-RF levels.
  
  
  CONCLUSIONS
  Measurement of HBeAg by CMIA is susceptible to negative interference from RFs. The level of IgG-RF played a key role in interfering with HBeAg CIMA and predominantly caused falsely low results. The pretreatment of samples with blocking reagents is therefore advisable prior to the interpretation of test results.
authors.forename: Liangcai
authors.initials: L
authors.lastname: Xie
authors.forename: Wenli
authors.initials: W
authors.lastname: Cheng
authors.forename: Lei
authors.initials: L
authors.lastname: Xu
authors.forename: Wen
authors.initials: W
authors.lastname: Fan
authors.forename: Yirong
authors.initials: Y
authors.lastname: Li
mesh_terms: D015415:Biomarkers / Q000097:blood; D005188:False Negative Reactions; D006509:Hepatitis B / Q000097:blood / Q000175:diagnosis / Q000276:immunology; D006513:Hepatitis B e Antigens / Q000097:blood* / Q000276:immunology; D006801:Humans; D007118:Immunoassay / Q000379:methods*; D007074:Immunoglobulin G / Q000097:blood* / Q000276:immunology; D008163:Luminescent Measurements; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D012217:Rheumatoid Factor / Q000097:blood* / Q000276:immunology
chemical_list: D015415:Biomarkers; D006513:Hepatitis B e Antigens; D007074:Immunoglobulin G; D012217:Rheumatoid Factor