title: DAS28-CRP and DAS28-ESR cut-offs for high disease activity in rheumatoid arthritis are not interchangeable.
abstract: BACKGROUND
  In most patients with rheumatoid arthritis (RA), Disease Activity Score 28-joint count C reactive protein (DAS28-CRP) is lower than DAS28 erythrocyte sedimentation rate (DAS28-ESR), suggesting that use of the DAS28-ESR cut-off to assess high disease activity (HDA) with DAS28-CRP may underestimate the number of patients with HDA. We determined the DAS28-CRP value corresponding to the validated DAS28-ESR cut-off for HDA.
  
  
  METHODS
  Baseline data were pooled from 2 clinical studies evaluating etanercept (ETN) plus methotrexate (MTX) or MTX in early RA; DAS28-CRP and DAS28-ESR were obtained, allowing the determination of the DAS28-CRP HDA value best corresponding to the DAS28-ESR cut-off of >5.1.
  
  
  RESULTS
  At baseline, as expected, fewer patients had HDA by DAS28-CRP than DAS28-ESR; DAS28-CRP>5.1 and DAS28-ESR>5.1 had only modest agreement (κ coefficients 0.45-0.54). Mean DAS28-CRP and DAS28-ESR were 5.7 and 6.2, respectively, in the ETN+MTX group (n=571), and 6.0 and 6.5 in the MTX group (n=262). A DAS28-CRP cut-off of 4.6 corresponded to a DAS28-ESR cut-off of 5.1.
  
  
  CONCLUSIONS
  We have shown that a DAS28-CRP of 4.6 corresponds to 5.1 for DAS28-ESR. Since this is substantially lower than the DAS28-ESR cut-off of 5.1, using 5.1 as the cut-off for DAS28-CRP underestimates disease activity in RA.
  
  
  BACKGROUND
  NCT00195494; NCT00913458.
authors.affiliation: University of Texas , Dallas, Texas , USA.
authors.forename: Roy M
authors.initials: RM
authors.lastname: Fleischmann
authors.affiliation: Leiden University Medical Center , Leiden , The Netherlands.
authors.forename: Désirée
authors.initials: D
authors.lastname: van der Heijde
authors.affiliation: Western Health and Social Care Trust , Londonderry , UK.
authors.forename: Philip V
authors.initials: PV
authors.lastname: Gardiner
authors.affiliation: inVentiv Health , Princeton, New Jersey , USA.
authors.forename: Annette
authors.initials: A
authors.lastname: Szumski
authors.affiliation: Pfizer , Collegeville, Pennsylvania , USA.
authors.forename: Lisa
authors.initials: L
authors.lastname: Marshall
authors.affiliation: Pfizer , Collegeville, Pennsylvania , USA.
authors.forename: Eustratios
authors.initials: E
authors.lastname: Bananis
keywords: Anti-TNF; DAS28; Rheumatoid Arthritis