[The anticitrulline antibody test: unsuitable for screening for rheumatoid arthritis]

In a recent study involving 691 patients, for whom general practitioners had ordered a rheumatoid factor test in 2004, the serum samples had simultaneously been analysed for antibodies against citrullinated fibrinogen. Two years later, 28 of 616 individuals of the original sample met the classification criteria for rheumatoid arthritis. In 8 of these 28 patients (29%), the rheumatoid factor test had been positive in 2004 and the anti-citrullinated fibrinogen test in 7 (25%) of the 28. The pre-test probability for rheumatoid arthritis was thus 5% and the post-test probability in case of a positive test for anti-citrullinated fibrinogen antibodies 37%. The pre-test probability for not having rheumatoid arthritis was 95% and the post-test probability in case of a negative test for anti-citrullinated fibrinogen antibodies 96%. In a patient sample with a low probability or incidence of rheumatoid arthritis, screening with these tests only moderately increases the chance of having rheumatoid arthritis in case of a positive test and adds virtually nothing to exclude rheumatoid arthritis.