Criteria developed for idiopathic inflammatory myopathies

(HealthDay)—New classification criteria have been developed for idiopathic inflammatory myopathies (IIM), according to an article published in the December issue of Arthritis & Rheumatology.

Ingrid E. Lundberg, M.D., Ph.D., from Karolinska University Hospital in Stockholm, and colleagues developed and validated new classification criteria for adult and juvenile IIM. Using published criteria and expert opinion, candidate variables were assembled; data were included from 47 rheumatology, dermatology, neurology, and pediatric clinics.

The researchers derived new criteria from 976 IIM patients and 624 non-IIM patients with mimicking conditions. Each item was given a weighted score; the total score corresponded to the likelihood of having IIM. A probability cutoff of 55 percent, representing a score of 5.5 (6.7 with muscle biopsy) was defined as probable IIM and had the best sensitivity and specificity (87 and 82 percent, respectively, without biopsies and 93 and 88 percent, respectively, with biopsies); this was recommended as the minimum to classify a patient with IIM. Definite IIM was defined based on a probability of ≥90 percent, corresponding to a score of ≥7.5 (≥8.7 with muscle biopsy). A probability of <50 percent, representing a score of <5.3 (<6.5 with muscle biopsy), ruled out IIM.

"The European League Against Rheumatism/American College of Rheumatology classification criteria for IIM have been endorsed by international rheumatology, dermatology, neurology, and pediatric groups," the authors write.

One author disclosed financial ties to the pharmaceutical industry.