Second, as the BSRBR was originally developed as a RA register, there are certain aspects of the patient's PsA that were not captured – such as the pattern of joint involvement (that is, axial or peripheral) and the Psoriasis Area and Severity Index scores, which may also have influenced the physician's decision on choice of anti-TNF agent as well as judgements about lack of efficacy. Here, TNF is linked to rheumatoid arthritis.