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Likelihood ratios as a function of antibody concentration for anti-cyclic citrullinated peptide antibodies and rheumatoid factor
  1. X Bossuyt1,
  2. D Coenen1,
  3. S Fieuws2,
  4. P Verschueren3,
  5. R Westhovens3,
  6. N Blanckaert1
  1. 1
    Laboratory Medicine, University Hospitals Leuven, Leuven, Belgium
  2. 2
    Biostatistics, Katholieke Universiteit Leuven, Leuven, Belgium
  3. 3
    Rheumatology, University Hospitals Leuven, Leuven, Belgium
  1. X Bossuyt, Laboratory Medicine, Immunology, University Hospitals Leuven, Herestraat 49, B-3000, Leuven, Belgium; xavier.bossuyt{at}

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Anti-cyclic citrullinated peptide (CCP) antibodies and rheumatoid factor (RF) are recommended screening tests for rheumatoid arthritis.1 In a meta-analysis,2 the sensitivity of anti-CCP (67%) for diagnosing rheumatoid arthritis was comparable to the sensitivity of RF (69%).2 The specificity of anti-CCP for rheumatoid arthritis (95%) was higher than the specificity of RF (85%).2 Consequently, the positive likelihood ratio was higher for anti-CCP (12.46) than for RF (4.86).2

Studies that addressed the clinical usefulness of anti-CCP used a single cut-off value and, hence, likelihood ratios were calculated based on a single cut-off. In the present letter, we illustrate how likelihood ratios for anti-CCP and RF …

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  • Competing interests: None declared.

  • Ethics approval: Ethics approval was obtained.

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