title: Significance of low level infliximab in the absence of anti-infliximab antibodies.
abstract: OBJECTIVE
  To evaluate the prevalence of double negative (DN) sera and the mechanisms responsible for DN status.
  
  
  METHODS
  Sera of inflammatory bowel disease patients treated with infliximab (IFX) were tested for drug/antibodies to infliximab (ATI) trough levels and the proportion of DN results was compared between a commercially available double antigen ELISA (with labeled IFX as the detection antibody) and an anti-lambda ELISA (with anti-human lambda chain detection antibody). Repeat testing with lower than customary serum dilution (1:10) was performed. Patients with DN status were matched with IFX+/ATI- controls and were followed-up for subsequent development of non-transient ATI to investigate if DN status precedes ATI.
  
  
  RESULTS
  Of 67 sera obtained at time of loss of response, only 6/67 (9%) were DN by anti-lambda ELISA compared to 27/67 (40%) with double antigen ELISA (P < 0.001, Fisher's Exact test). Of the latter 27 sera, 22% were also DN by anti-lambda ELISA, whereas 44% were actually IFX positive (IFX+ATI-), 30% were ATI positive (IFX-ATI+) and 4% were double positive (IFX+ATI+). Re-testing using a 1:10 dilution converted most DN results into IFX+ and /or ATI+ status. Patients with DN status had shorter survival free of non-transient ATI compared with matched controls (log rank test, P < 0.001). In 9/30 (30%) of these patients, non transient ATI occurred before and after the event at which the DN serum was obtained, supporting the view that a DN result may represent a particular time-point along the two curves of ATI titer rise and infliximab drug level decline.
  
  
  CONCLUSIONS
  DN status may result from false negative detection of IFX or ATI by double antigen ELISA, suggesting a transitional state of low-level immunogenicity, rather than non-immunological clearance.
authors: Bella Ungar, Adi Anafy, Miri Yavzori, Orit Picard, Ella Fudim, Uri Kopylov, Rami Eliakim, Shomron Ben-Horin, Department of Gastroenterology, Sheba Medical Center Tel Hashomer and Sackler School of Medicine, Tel-Aviv University, Tel-Aviv 6997801, Israel.
authors: Bella
authors: B
authors: Ungar
authors: Bella Ungar, Adi Anafy, Miri Yavzori, Orit Picard, Ella Fudim, Uri Kopylov, Rami Eliakim, Shomron Ben-Horin, Department of Gastroenterology, Sheba Medical Center Tel Hashomer and Sackler School of Medicine, Tel-Aviv University, Tel-Aviv 6997801, Israel.
authors: Adi
authors: A
authors: Anafy
authors: Bella Ungar, Adi Anafy, Miri Yavzori, Orit Picard, Ella Fudim, Uri Kopylov, Rami Eliakim, Shomron Ben-Horin, Department of Gastroenterology, Sheba Medical Center Tel Hashomer and Sackler School of Medicine, Tel-Aviv University, Tel-Aviv 6997801, Israel.
authors: Henit
authors: H
authors: Yanai
authors: Bella Ungar, Adi Anafy, Miri Yavzori, Orit Picard, Ella Fudim, Uri Kopylov, Rami Eliakim, Shomron Ben-Horin, Department of Gastroenterology, Sheba Medical Center Tel Hashomer and Sackler School of Medicine, Tel-Aviv University, Tel-Aviv 6997801, Israel.
authors: Yulia
authors: Y
authors: Ron
authors: Bella Ungar, Adi Anafy, Miri Yavzori, Orit Picard, Ella Fudim, Uri Kopylov, Rami Eliakim, Shomron Ben-Horin, Department of Gastroenterology, Sheba Medical Center Tel Hashomer and Sackler School of Medicine, Tel-Aviv University, Tel-Aviv 6997801, Israel.
authors: Miri
authors: M
authors: Yavzori
authors: Bella Ungar, Adi Anafy, Miri Yavzori, Orit Picard, Ella Fudim, Uri Kopylov, Rami Eliakim, Shomron Ben-Horin, Department of Gastroenterology, Sheba Medical Center Tel Hashomer and Sackler School of Medicine, Tel-Aviv University, Tel-Aviv 6997801, Israel.
authors: Orit
authors: O
authors: Picard
authors: Bella Ungar, Adi Anafy, Miri Yavzori, Orit Picard, Ella Fudim, Uri Kopylov, Rami Eliakim, Shomron Ben-Horin, Department of Gastroenterology, Sheba Medical Center Tel Hashomer and Sackler School of Medicine, Tel-Aviv University, Tel-Aviv 6997801, Israel.
authors: Ella
authors: E
authors: Fudim
authors: Bella Ungar, Adi Anafy, Miri Yavzori, Orit Picard, Ella Fudim, Uri Kopylov, Rami Eliakim, Shomron Ben-Horin, Department of Gastroenterology, Sheba Medical Center Tel Hashomer and Sackler School of Medicine, Tel-Aviv University, Tel-Aviv 6997801, Israel.
authors: Ronen
authors: R
authors: Loebstein
authors: Bella Ungar, Adi Anafy, Miri Yavzori, Orit Picard, Ella Fudim, Uri Kopylov, Rami Eliakim, Shomron Ben-Horin, Department of Gastroenterology, Sheba Medical Center Tel Hashomer and Sackler School of Medicine, Tel-Aviv University, Tel-Aviv 6997801, Israel.
authors: Uri
authors: U
authors: Kopylov
authors: Bella Ungar, Adi Anafy, Miri Yavzori, Orit Picard, Ella Fudim, Uri Kopylov, Rami Eliakim, Shomron Ben-Horin, Department of Gastroenterology, Sheba Medical Center Tel Hashomer and Sackler School of Medicine, Tel-Aviv University, Tel-Aviv 6997801, Israel.
authors: Yehuda
authors: Y
authors: Chowers
authors: Bella Ungar, Adi Anafy, Miri Yavzori, Orit Picard, Ella Fudim, Uri Kopylov, Rami Eliakim, Shomron Ben-Horin, Department of Gastroenterology, Sheba Medical Center Tel Hashomer and Sackler School of Medicine, Tel-Aviv University, Tel-Aviv 6997801, Israel.
authors: Iris
authors: I
authors: Dotan
authors: Bella Ungar, Adi Anafy, Miri Yavzori, Orit Picard, Ella Fudim, Uri Kopylov, Rami Eliakim, Shomron Ben-Horin, Department of Gastroenterology, Sheba Medical Center Tel Hashomer and Sackler School of Medicine, Tel-Aviv University, Tel-Aviv 6997801, Israel.
authors: Rami
authors: R
authors: Eliakim
authors: Bella Ungar, Adi Anafy, Miri Yavzori, Orit Picard, Ella Fudim, Uri Kopylov, Rami Eliakim, Shomron Ben-Horin, Department of Gastroenterology, Sheba Medical Center Tel Hashomer and Sackler School of Medicine, Tel-Aviv University, Tel-Aviv 6997801, Israel.
authors: Shomron
authors: S
authors: Ben-Horin
mesh_terms: D000911:Antibodies, Monoclonal / Q000097:blood / Q000276:immunology* / Q000493:pharmacokinetics*; D015415:Biomarkers / Q000097:blood; D016022:Case-Control Studies; D016903:Drug Monitoring; D004797:Enzyme-Linked Immunosorbent Assay; D005188:False Negative Reactions; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood*; D007166:Immunosuppressive Agents / Q000097:blood / Q000276:immunology* / Q000493:pharmacokinetics*; D015212:Inflammatory Bowel Diseases / Q000097:blood / Q000175:diagnosis / Q000188:drug therapy* / Q000276:immunology; D000069285:Infliximab; D007557:Israel; D011237:Predictive Value of Tests; D012698:Serologic Tests; D013997:Time Factors; D014409:Tumor Necrosis Factor-alpha / Q000037:antagonists & inhibitors
chemical_list: D000911:Antibodies, Monoclonal; D015415:Biomarkers; D007074:Immunoglobulin G; D007166:Immunosuppressive Agents; D014409:Tumor Necrosis Factor-alpha; D000069285:Infliximab
keywords: Biological therapy; Drug response; Immunology; Inflammatory bowel disease; Infliximab