Rheumatoid factor by laser nephelometry and Waaler-Rose assay: prognostic value in patients with recent-onset rheumatoid arthritis.
OBJECTIVE
To evaluate the prognostic value of rheumatoid factor (RF), detected in the Waaler-Rose agglutination assay and by nephelometry, in patients with recent-onset rheumatoid arthritis (RA).


METHODS
Consecutive patients with new-onset RA between 1993 and 1997 were followed for a median period of 4.7 years. Clinical data at baseline and drug use during the disease course were recorded. Outcome parameters studied were disease process, damage (erosions, joint surgery, extra-articular manifestations, and new co-morbidity), and death. Cut-off levels for RF were >40 IU/mL (nephelometry) and titres 1:160 (Waaler-Rose haemagglutination).


RESULTS
RF tests were negative by both methods in 22% of RA patients (RF- group), while 33% were RF positive by nephelometry only (RF+ group) and 45% were positive by Waaler-Rose and nephelometry (RF++ group). Baseline clinical and laboratory findings as well as the number of subsequently used disease-modifying anti-rheumatic drugs (DMARDs), the number of patients starting and the time spent on steroid therapy were similar in the three RF groups. Odd ratios for death (n = 23), erosions (n = 62), and serious extra-articular disease manifestations (EAMs) (n = 13) as well as patient survival, erosion-free or surgery-free survival rates did not differ between the RF groups. Only rheumatoid nodules were more frequent in RF++ patients.


CONCLUSIONS
The baseline presence of RF by either Waaler-Rose or nephelometry was not associated with differences in drug therapy, morbidity other than rheumatoid nodules, or mortality in RA patients in the first 5 years of disease. Being immunoglobulin M (IgM) RF positive thus had little impact on RA patient outcome.
Nikolaisen
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C
Department of Rheumatology, Institute of Clinical Medicine, University of Tromsø, Norway. cathrin.nikolaisen@unn.no
Rekvig
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OP
Nossent
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HC
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000372:Agglutination Tests / Q000379:methods; D018501:Antirheumatic Agents / Q000627:therapeutic use*; D001172:Arthritis, Rheumatoid / Q000175:diagnosis* / Q000188:drug therapy* / Q000401:mortality; D015415:Biomarkers / Q000032:analysis; D015331:Cohort Studies; D016001:Confidence Intervals; D018450:Disease Progression; D005260:Female; D006801:Humans; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D009391:Nephelometry and Turbidimetry / Q000379:methods; D009664:Norway; D011379:Prognosis; D012189:Retrospective Studies; D012217:Rheumatoid Factor / Q000032:analysis*; D012218:Rheumatoid Nodule / Q000175:diagnosis / Q000188:drug therapy / Q000401:mortality; D012307:Risk Factors; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index; D015996:Survival Rate; D013997:Time Factors; D016896:Treatment Outcome
D018501:Antirheumatic Agents; D015415:Biomarkers; D012217:Rheumatoid Factor