Likelihood ratios as a function of antibody concentration for anti-cyclic citrullinated peptide antibodies and rheumatoid factor

X Bossuyt¹, D Coenen¹, S Fieuws², P Verschueren³, R Westhovens³, N Blanckaert¹

¹ Laboratory Medicine, University Hospitals Leuven, Leuven, Belgium
² Biostatistics, Katholieke Universiteit Leuven, Leuven, Belgium
³ Rheumatology, University Hospitals Leuven, Leuven, Belgium

Correspondence to:
X Bossuyt, Laboratory Medicine, Immunology, University Hospitals Leuven, Herestraat 49, B-3000, Leuven, Belgium; xavier.bossuyt@uz.kuleuven.ac.be

Accepted 7 April 2008

The first 150 words of the full text of this article appear below.

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 depend on the antibody level. Our calculations were based on a clinically well defined group of patients with rheumatoid arthritis (n = 85), diseased controls (n = 165) (including psoriatic arthritis, connective tissue disease and organ specific autoimmune diseases), and a group of consecutive patients for whom . . . [Full text of this article]

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This article has been cited by other articles:

• BYKERK, V. (2009). Anti-Cyclic Citrullinated Peptide Antibody versus HAQ/MDHAQ: Comparing Apples and Oranges?. The Journal of Rheumatology 36: 1565-1567 [Full Text]