title: Anti-adalimumab antibodies and adalimumab concentrations in psoriatic arthritis; an association with disease activity at 28 and 52 weeks of follow-up.
abstract: OBJECTIVE
  To investigate the relationship between antidrug antibodies (ADA), adalimumab concentrations and clinical response in patients with psoriatic arthritis (PsA) during 52 weeks of follow-up.
  
  
  METHODS
  This prospective cohort study included 103 consecutive patients with PsA. Disease Activity Score of 28 joints (DAS28), Erythrocyte Sedimentation Rate, C reactive protein and Psoriasis Area and Severity Index were assessed. Adalimumab concentrations and ADA were measured in serum trough samples, using an ELISA and a radio immunoassay, respectively.
  
  
  RESULTS
  Adalimumab concentrations were significantly lower at 28 and 52 weeks in patients with detectable ADA compared with patients without detectable ADA (at week 28: 1.3 mg/L (IQR 0.0-3.2) versus 8.7 mg/L (IQR 5.7-11.5), p<0.001; at week 52: 0.9 mg/L (IQR 0.0-2.9) vs 9.4 mg/L (IQR 5.7-12.1), p=0.0001). DAS28 at 28 weeks (2.16 vs 2.95, p=0.023) and 52 weeks (2.19 vs 2.95, p=0.024) showed a significant difference; patients with detectable ADA had a poorer clinical outcome than patients without.
  
  
  CONCLUSIONS
  Patients with detectable ADA had lower adalimumab concentrations and a significantly poorer clinical outcome compared with patients in whom ADA were not detected.
authors.affiliation: Department of Rheumatology, Jan van Breemen Research Institute | Reade, Amsterdam, The Netherlands.
authors.forename: Erik H
authors.initials: EH
authors.lastname: Vogelzang
authors.affiliation: Department of Rheumatology, Jan van Breemen Research Institute | Reade, Amsterdam, The Netherlands.
authors.forename: Eva L
authors.initials: EL
authors.lastname: Kneepkens
authors.affiliation: Department of Rheumatology, Jan van Breemen Research Institute | Reade, Amsterdam, The Netherlands.
authors.forename: Michael T
authors.initials: MT
authors.lastname: Nurmohamed
authors.affiliation: Department of Rheumatology, Jan van Breemen Research Institute | Reade, Amsterdam, The Netherlands.
authors.forename: Arno W R
authors.initials: AW
authors.lastname: van Kuijk
authors.affiliation: Department of Immunopathology, Sanquin, Amsterdam, The Netherlands.
authors.forename: Theo
authors.initials: T
authors.lastname: Rispens
authors.affiliation: Department of Rheumatology, Jan van Breemen Research Institute | Reade, Amsterdam, The Netherlands Department of Immunopathology, Sanquin, Amsterdam, The Netherlands.
authors.forename: Gertjan
authors.initials: G
authors.lastname: Wolbink
authors.affiliation: Department of Rheumatology, Jan van Breemen Research Institute | Reade, Amsterdam, The Netherlands.
authors.forename: Charlotte L M
authors.initials: CL
authors.lastname: Krieckaert
mesh_terms: D000068879:Adalimumab; D000328:Adult; D000906:Antibodies / Q000276:immunology*; D061067:Antibodies, Monoclonal, Humanized / Q000097:blood / Q000276:immunology* / Q000627:therapeutic use; D018501:Antirheumatic Agents / Q000097:blood / Q000276:immunology* / Q000627:therapeutic use; D015535:Arthritis, Psoriatic / Q000097:blood / Q000188:drug therapy*; D015331:Cohort Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012720:Severity of Illness Index; D016896:Treatment Outcome
chemical_list: D000906:Antibodies; D061067:Antibodies, Monoclonal, Humanized; D018501:Antirheumatic Agents; D000068879:Adalimumab