Missing Anticitrullinated Protein Antibody Does Not Affect Short-term Outcomes in Early Inflammatory Arthritis: From the Canadian Early Arthritis Cohort.
OBJECTIVE
Anticitrullinated protein antibody (ACPA) is as sensitive as, but more specific than, rheumatoid factor (RF) and is detected earlier in rheumatoid arthritis (RA). Although part of the RA classification criteria, ACPA testing is not routinely paid for/accessible in all jurisdictions. The effect of missing ACPA testing was studied to determine whether failure to perform ACPA testing could cause a care gap in early inflammatory arthritis.


METHODS
Nearly 2000 patients (n = 1998) recruited to an early inflammatory arthritis cohort were allocated into 3 groups: (1) seropositive (either RF+ or ACPA+), (2) seronegative (RF- and ACPA-), and (3) missing ACPA and RF-. Analyses were adjusted for age, sex, symptom duration, and smoking status if p < 0.1. Disease Activity Score at 28 joints (DAS28) at 3 months was studied, because beyond then, disease activity is expected to determine ongoing treatment.


RESULTS
More seropositive patients fulfilled the 2010 American College of Rheumatology/European League Against Rheumatism RA criteria than seronegative patients. Group 3 was slightly older and had a smaller percentage of females, as well as shorter symptom duration and less smoking. At 3 months, group 3 was treated with fewer disease-modifying antirheumatic drugs and methotrexate (p < 0.00002) than groups 1 and 2, but there were no significant differences in DAS28, Health Assessment Questionnaire-Disability Index (HAQ-DI), proportion receiving corticosteroids, or physician's/patient's global assessments.


CONCLUSIONS
There was no care gap in the RF-negative, unknown ACPA group because there were no significant differences in the DAS28, 3-month change in DAS28, or HAQ-DI, despite less treatment. Cost-effectiveness of ensuring ACPA testing availability in suspected RA is unknown because early outcomes did not differ, whether or not ACPA was available.
Jenny
J
Shu
Vivian P
VP
Bykerk
Gilles
G
Boire
Boulos
B
Haraoui
Carol
C
Hitchon
J Carter
JC
Thorne
Diane
D
Tin
Edward C
EC
Keystone
Janet E
JE
Pope
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D000888:Antibodies, Anti-Idiotypic / Q000097:blood*; D018501:Antirheumatic Agents / Q000627:therapeutic use*; D001172:Arthritis, Rheumatoid / Q000097:blood / Q000188:drug therapy* / Q000276:immunology*; D002170:Canada; D016009:Chi-Square Distribution; D015331:Cohort Studies; D004305:Dose-Response Relationship, Drug; D004334:Drug Administration Schedule; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D016017:Odds Ratio; D010456:Peptides, Cyclic / Q000097:blood*; D011446:Prospective Studies; D012217:Rheumatoid Factor / Q000097:blood*; D012720:Severity of Illness Index; D013997:Time Factors; D016896:Treatment Outcome; D055815:Young Adult
D000888:Antibodies, Anti-Idiotypic; D018501:Antirheumatic Agents; D010456:Peptides, Cyclic; C487763:cyclic citrullinated peptide; D012217:Rheumatoid Factor
ANTICITRULLINATED PROTEIN ANTIBODY; CYCLIC CITRULLINATED PEPTIDE ANTIBODIES; EARLY RHEUMATOID ARTHRITIS; MISSING DATA; RHEUMATOID FACTOR