title: On optimizing the blocking step of indirect enzyme-linked immunosorbent assay for Epstein-Barr virus serology.
abstract: BACKGROUND
  Because blocking agent occupies most binding surface of a solid phase, its ability to prevent nonspecific binding determines the signal-to-noise ratio (SNR) and reliability of an enzyme-linked immunosorbent assay (ELISA).
  
  
  METHODS
  We demonstrate a stepwise approach to seek a compatible blocking buffer for indirect ELISA, via a case-control study (n=176) of Epstein-Barr virus (EBV)-associated nasopharyngeal carcinoma (NPC).
  
  
  RESULTS
  Regardless of case-control status, we found that synthetic polymer blocking agents, mainly Ficoll and poly(vinyl alcohol) (PVA) were able to provide homogeneous backgrounds among samples, as opposed to commonly used blocking agents, notably nonfat dry milk (NFDM). The SNRs for NPC samples that correspond to blocking using PVA were approximately 3-fold, on average, higher than those blocking using NFDM. Both intra- and inter-assay precisions of PVA-based assays were <14%.
  
  
  CONCLUSIONS
  A blocking agent of choice should have tolerable sample backgrounds from both cases and controls to ensure the reliability of an immunoassay.
authors.affiliation: Institute of Biological Sciences, Faculty of Science, University of Malaya, 50603 Kuala Lumpur, Malaysia.
authors.forename: Chun Shen
authors.initials: CS
authors.lastname: Lim
authors.forename: Gopala
authors.initials: G
authors.lastname: Krishnan
authors.forename: Choon Kook
authors.initials: CK
authors.lastname: Sam
authors.forename: Ching Ching
authors.initials: CC
authors.lastname: Ng
mesh_terms: D000818:Animals; D000914:Antibodies, Viral / Q000737:chemistry / Q000276:immunology; D002277:Carcinoma; D016022:Case-Control Studies; D057075:Enzyme Assays / Q000592:standards*; D004797:Enzyme-Linked Immunosorbent Assay / Q000592:standards*; D020031:Epstein-Barr Virus Infections / Q000175:diagnosis* / Q000276:immunology; D019309:Epstein-Barr Virus Nuclear Antigens / Q000032:analysis*; D005362:Ficoll / Q000737:chemistry; D004854:Herpesvirus 4, Human / Q000276:immunology / Q000302:isolation & purification*; D006801:Humans; D008892:Milk / Q000737:chemistry; D000077274:Nasopharyngeal Carcinoma; D009303:Nasopharyngeal Neoplasms / Q000175:diagnosis* / Q000276:immunology; D015588:Observer Variation; D011142:Polyvinyl Alcohol / Q000737:chemistry; D059629:Signal-To-Noise Ratio
chemical_list: D000914:Antibodies, Viral; D019309:Epstein-Barr Virus Nuclear Antigens; D005362:Ficoll; D011142:Polyvinyl Alcohol