Autoantibody profiling in patients with very early rheumatoid arthritis: a follow-up study.
OBJECTIVE
To investigate time courses of autoantibody profiles in patients with early arthritis.


METHODS
A total of 200 patients with very early arthritis (<3 months duration), among them 102 patients with a final diagnosis of rheumatoid arthritis (RA) and 98 with other rheumatic diseases, were followed up for several years. First follow-up testing was performed in all patients (mean 5 months from baseline), and 82 patients with RA and 35 patients without RA were available for last follow-up testing (mean 32 months from baseline). IgM-rheumatoid factor (RF) was measured by nephelometry, IgA-RF, IgG-RF and anti-cyclic citrullinated peptide antibodies (ACPA) by ELISA, and anti-RA33 antibodies were determined by immunoblotting.


RESULTS
At baseline, IgA-RF was detectable in 29% and IgG-RF in 14% of patients with RA while IgM-RF>50 IU/ml (RF50) was positive in 45% of the patients; specificities were 97%, 99% and 96%, respectively. However, the vast majority of patients positive for IgA-RF or IgG-RF were also positive for RF50 or ACPA. During follow-up, the prevalence of ACPA slightly increased while prevalence of all RF subtypes and anti-RA33 decreased. Remarkably, the number of patients positive for RF50 and/or ACPA remained constant, and these patients had a highly increased risk for developing erosive disease in contrast to patients solely positive for anti-RA33.


CONCLUSIONS
Testing for RF subtypes did not provide additional diagnostic information. Patients positive for RF50 and/or ACPA had an unfavourable prognosis, irrespectively of changes in the antibody profile during follow-up, whereas anti-RA33 positivity was inversely associated with erosiveness at baseline and at later time points.
Nell-Duxneuner
V
V
Division of Rheumatology, Department of Internal Medicine III, Medical University of Vienna, A-1090 Vienna, Austria.
Machold
K
K
Stamm
T
T
Eberl
G
G
Heinzl
H
H
Hoefler
E
E
Smolen
J S
JS
Steiner
G
G
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000974:Antibodies, Antinuclear / Q000097:blood; D001172:Arthritis, Rheumatoid / Q000175:diagnosis / Q000276:immunology*; D001323:Autoantibodies / Q000097:blood*; D015415:Biomarkers / Q000097:blood; D018450:Disease Progression; D005260:Female; D005500:Follow-Up Studies; D034481:Heterogeneous-Nuclear Ribonucleoprotein Group A-B / Q000276:immunology; D006801:Humans; D007075:Immunoglobulin M / Q000097:blood; D008297:Male; D008875:Middle Aged; D010456:Peptides, Cyclic / Q000276:immunology; D011379:Prognosis; D012217:Rheumatoid Factor / Q000097:blood; D055815:Young Adult
D000974:Antibodies, Antinuclear; D001323:Autoantibodies; D015415:Biomarkers; D034481:Heterogeneous-Nuclear Ribonucleoprotein Group A-B; D007075:Immunoglobulin M; D010456:Peptides, Cyclic; C487763:cyclic citrullinated peptide; D012217:Rheumatoid Factor