New classification criteria offers faster, more accurate path to diagnosing myositis diseases

The ability to diagnose myositis diseases and treat them properly just improved immensely. For more than 40 years, the criteria physicians have used to diagnose most myositis diseases has been based on expert opinion, not hard science.

The most frequently used guidelines are known as the "Bohan and Peter criteria." They combine physical symptoms with information from laboratory and other tests to define polymyositis (PM) and dermatomyositis (DM). But they do not recognize inclusion body myositis (IBM), necrotizing myopathy (NM), or amyopathic dermatomyositis (ADM). They may also erroneously identify as myositis some muscular dystrophies, which are not inflammatory in nature.

The good news is that recently a group of myositis researchers from around the world set out to develop a wholly new set of classification criteria for adult and juvenile myositis diseases based on data from more 1,600 patients (972 with myositis, 624 comparators). The results of this years-long effort has just been published along with a web-based calculator that can be used, with or without biopsy data, to determine the probability of a particular diagnosis based on statistical data.

This evidence-based, approach developed through analysis of a large patient base, offers a faster, more accurate path to diagnosing myositis diseases and treating them properly, which will spare patients a great deal of anxiety and suffering. These classification criteria can also be used in clinical research to more accurately identify patient cohorts and will generate more useful research findings.

Not only are these new classification criteria a breakthrough that will enable progress in the diagnosis and treatment of myositis diseases and research, they also represent a monumental achievement of international and interdisciplinary scientific cooperation. The Myositis Association helped to fund this effort and applauds the 100 myositis experts of the International Myositis Classification Criteria Project (IMCCP) that produced this milestone achievement, which will have a lasting impact on those who live with myositis.