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Table 3 Sensitivity and specificity of rheumatoid factor

From: Autoantibodies in rheumatoid arthritis and their clinical significance

  Rheumatoid factor (% positive patients)*
Diagnosis ≥ 15 U/ml ≥ 50 U/ml ≥ 100 U/ml
Rheumatoid arthritis 66 46 26
Sjögren's syndrome 62 52 33
SLE 27 10 3
MCTD 23 13 6
Scleroderma 44 18 2
Polymyositis 18 0 0
Reactive arthritis 0 0 0
Osteoarthritis 25 4 4
Healthy controls 13 0 0
Sensitivity (%) 66 46 26
Specificity (%) 72 88 (92) 95 (98)
  1. SLE, systemic lupus erythematosus; MCTD, mixed connective tissue disease. * Rheumatoid factor was determined by nephelogmetry in 100 patients with RA, in more than 200 patients with other rheumatic disease, and in 30 healthy controls. Specificity when a diagnosis of Sjögren's syndrome can be excluded.