Routine interferon-neutralising antibody testing in patients with relapsing-remitting multiple sclerosis.

Multiple sclerosis is a leading cause of disability in young adults, with the Scottish population suffering the highest prevalence in Europe. Disease-modifying therapies, including beta-interferon (IFN-ß), are increasingly used to minimise relapse frequency in the majority of patients who present with a relapsing-remitting disease pattern. Unfortunately, neutralising antibodies (NABs) may develop against IFN-ß and are associated with reduced efficacy. These antibodies may be detected using a serum sample. Despite the importance of this problem, from both a patient's perspective and a wider community and economic standpoint, there is no universally agreed protocol for the use of NAB testing. Authorities variously suggest routine 'screening' testing or, conversely, testing only in specific situations. In Scotland, routine testing is seldom used. We report our experience of routine NAB testing in 105 patients (of whom 35 were NAB-positive) over two years in NHS Tayside and comment on its cost and implications.