Dr. Christiansen, et al, reply

To the Editor: We thank Dr. Sabour1 and Dr. Rothschild2 for their interest in our manuscript3.We acknowledge that κ statistics depend on the prevalence of the variable under investigation and we have made this transparent. This limitation becomes relevant when comparing results across multiple studies. However, we use κ to assess which of several variables similarly assessed on the same patients provide sufficient agreement, i.e., we primarily used κ to order lesion types. This implies that the actual value of κ is of minor importance and the above limitation does not alter the conclusion of … Address correspondence to Dr. A.A. Christiansen, Department of Research, King Christian 10th Hospital for Rheumatic Diseases, Toldbodgade 3, 6300 Grasten, Denmark. E-mail: achristiansen{at}gigtforeningen.dk