Thresholds for the 28-joint disease activity score (DAS28) using C-reactive protein are lower compared to DAS28 using erythrocyte sedimentation rate in early rheumatoid arthritis.
OBJECTIVE
The 28-Joint Disease Activity Score (DAS28) using C-reactive protein (CRP) and DAS28 using erythrocyte sedimentation rate (DAS28-ESR) may not be interchangeable. We sought to compare and estimate optimal thresholds for the DA28-CRP for use in early rheumatoid arthritis (ERA).


METHODS
Patients from the Canadian Early Arthritis Cohort with baseline and 12 months' data for both DAS28-ESR and DAS28-CRP were examined for correlations and differences between DAS28-CRP and DAS28-ESR across their range of values. Receiver operating characteristic analysis identified thresholds for DAS28-CRP that best corresponded to established thresholds for the DAS28-ESR using the total sample, then stratified by age and sex. Agreement between DAS28-CRP and DAS28-ESR thresholds was assessed with the kappa statistic.


RESULTS
The sample included 995 patients with mean (SD) age of 53.7 (14.5) years, 5.8 (2.9) months of symptom duration and 74% were female. DAS28-CRP and DAS28-ESR scores were highly correlated (r= 0.92, p<0.0001), however DAS28-CRP values were consistently lower than DAS28-ESR values. Calculated thresholds for DAS28-CRP were lower with 2.5 for remission, 2.9 for low disease activity, and 4.6 for high disease activity but showed moderate agreement with the DAS28-ESR thresholds (kappa=0.70).


CONCLUSIONS
In this large sample of ERA patients, newly estimated thresholds for DAS28-CRP were consistently lower than DAS28-ESR thresholds across the spectrum of disease activity. This may have important clinical implications if inflammatory markers are used interchangeably. Additional external validation of our findings is needed.
Sinai Health System, University of Toronto, Canada. bindee.kuriya@sinaihealthsystem.ca.
Bindee
B
Kuriya
Division of Epidemiology, University of Toronto, Dalla Lana School of Public Health, Toronto, Canada.
Orit
O
Schieir
Sinai Health System, University of Toronto, Canada.
Daming
D
Lin
Sinai Health System, University of Toronto, Canada.
Juan
J
Xiong
St. Josephs Health Care, University of Western Ontario, London, Canada.
Janet
J
Pope
Université de Sherbrooke, Canada.
Gilles
G
Boire
Institut de Rhumatologie, Montreal, Canada.
Boulos
B
Haraoui
Southlake Regional Health Centre, Newmarket, Canada.
John Carter
JC
Thorne
Southlake Regional Health Centre, Newmarket, Canada.
Diane
D
Tin
University of Manitoba, Winnipeg, Canada.
Carol
C
Hitchon
Vancouver General Hospital, University of British Columbia, Canada.
Shahin
S
Jamal
Sinai Health System, University of Toronto, Canada.
Edward
E
Keystone
Sinai Health System, University of Toronto, Canada; and Hospital for Special Surgery, New York, USA.
Vivien P
VP
Bykerk
D000328:Adult; D017677:Age Distribution; D000368:Aged; D019540:Area Under Curve; D001172:Arthritis, Rheumatoid / Q000097:blood / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000188:drug therapy; D015415:Biomarkers / Q000097:blood; D001799:Blood Sedimentation; D002097:C-Reactive Protein / Q000378:metabolism*; D002170:Canada; D004185:Disability Evaluation; D005260:Female; D006801:Humans; D018836:Inflammation Mediators / Q000097:blood*; D007596:Joints / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D012372:ROC Curve; D012074:Remission Induction; D015203:Reproducibility of Results; D012720:Severity of Illness Index; D017678:Sex Distribution; D013997:Time Factors; D016896:Treatment Outcome
D015415:Biomarkers; D018836:Inflammation Mediators; D002097:C-Reactive Protein