title: Complement system in psoriatic arthritis: a useful marker in response prediction and monitoring of anti-TNF treatment.
abstract: OBJECTIVE
  Treatment with anti-TNF agents is well established in psoriatic arthritis (PsA). Anti-TNF agents are capable of modulating complement activity in vitro but there are no data on the in vivo effect. Anti-TNF have high costs and potential risks, thus, there is an urgent need for accurate predictors of response. We aimed at studying the usefulness of erythrocyte-sedimentation-rate (ESR), C-reactive protein (CRP), and complement for response prediction and monitoring of anti-TNF treatment in PsA patients.
  
  
  METHODS
  Fifty-five patients were included consecutively before starting etanercept or adalimumab. ESR, CRP, plasma complement C3, C4, and C3 and B cleavage fragments were evaluated at baseline and after 22 weeks of anti-TNF treatment. Disease activity was measured with DAS28 and response to therapy with EULAR criteria. Complement was evaluated at baseline in 30 healthy subjects as well.
  
  
  RESULTS
  At baseline, C3 and C4 levels were significantly higher than in controls (C3 126.9±22 vs. 110±25 mg/dl, p=0.000002; C4 31.2±9.2 vs. 22.7±8.3 mg/dl, p=0.0003). After anti-TNF therapy, C3 and C4 levels were significantly reduced to normalization (p=0.0009 and 0.0005, respectively) and ESR, CRP and DAS28 showed a significant reduction (p=0.002, 0.004 and 0.0001, respectively). Split products of C3 and B were not observed at baseline and after 22 weeks. Higher baseline C3 levels were associated with EULAR non-response (p=0.011).
  
  
  CONCLUSIONS
  PsA patients with moderate to severe disease show elevated C3 and C4 levels, reverted by anti-TNF treatment. High C3 may be considered a hallmark of inflammation and C3 revealed the highest predictive value for response to anti-TNF.
authors.affiliation: Allergology, Clinical Immunology and Rheumatology, Department of Internal Medicine, University of Rome Tor Vergata, Rome, Italy.
authors.forename: M S
authors.initials: MS
authors.lastname: Chimenti
authors.forename: C
authors.initials: C
authors.lastname: Perricone
authors.forename: D
authors.initials: D
authors.lastname: Graceffa
authors.forename: G
authors.initials: G
authors.lastname: Di Muzio
authors.forename: E
authors.initials: E
authors.lastname: Ballanti
authors.forename: M D
authors.initials: MD
authors.lastname: Guarino
authors.forename: P
authors.initials: P
authors.lastname: Conigliaro
authors.forename: E
authors.initials: E
authors.lastname: Greco
authors.forename: B
authors.initials: B
authors.lastname: Kroegler
authors.forename: R
authors.initials: R
authors.lastname: Perricone
mesh_terms: D000328:Adult; D000368:Aged; D018501:Antirheumatic Agents / Q000627:therapeutic use; D015535:Arthritis, Psoriatic / Q000188:drug therapy / Q000276:immunology*; D002097:C-Reactive Protein; D003165:Complement System Proteins / Q000378:metabolism*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D012720:Severity of Illness Index; D016896:Treatment Outcome; D014409:Tumor Necrosis Factor-alpha / Q000037:antagonists & inhibitors
chemical_list: D018501:Antirheumatic Agents; D014409:Tumor Necrosis Factor-alpha; D003165:Complement System Proteins; D002097:C-Reactive Protein