This disclosure relates to the field of diagnostic methods. A new marker antibody for rheumatoid arthritis, as well as a new method for detecting rheumatoid arthritis, is disclosed herein. Also provided herein are means and methods for predicting whether a subject will develop rheumatoid arthritis. This disclosure is based on the discovery that patients with rheumatoid arthritis have antibodies in their circulation that react specifically with citrullinated antibodies. In one aspect, the disclosure, therefore, relates to an antibody comprising a citrulline residue. In another aspect, the disclosure provides a method for the detection of antibodies specific for rheumatoid arthritis in a sample from a subject, wherein the sample is contacted with a citrullinated antibody and wherein it is determined whether the sample comprises antibodies specifically reactive with the citrullinated antibody.
