Proposal for a new set of classification criteria for adult-onset Still disease

Adult-onset Still disease (AOSD) is a rare rheumatic disease, for which several sets of classification criteria have been proposed. None can be considered a gold standard in clinical research. The present study aimed to define a better classification criteria set, including more recent markers than those previously used. We retrospectively reviewed the medical charts of 207 patients who had ferritin and glycosylated ferritin measured at the biochemistry laboratory of Bichat Hospital, Paris, France. Data present at the time of diagnosis were extracted, and diagnosis was assigned according to a standardized procedure. Seventy-two AOSD patients and 130 controls, suffering from systemic, neoplastic, infectious, or hepatic diseases, were included. Eight criteria for the new classification set were selected using a multiple logistic regression: spiking fever ≥39 °C, arthralgia, maculopapular rash, transient erythema, pharyngitis, leukocyte count ≥10,000/mm3, polymorphonuclear count ≥80%, glycosylated ferritin ≤20%. The selected variables were classified into minor (maculopapular rash and leukocytes ≥10,000/mm3) and major criteria (the 6 others); to retain the diagnosis of AOSD, 4 major criteria or 3 major + 2 minor were needed. This set provided a sensitivity of 80.6% and a specificity of 98.5%, which is higher than those obtained with previous sets. The discriminative power of the model has been confirmed with a receiver operating characteristic (ROC) curve, which displayed an area under the curve of 0.973, close to 1. This new classification criteria set seems more powerful than the previous published sets, without requiring exclusion criteria. After validation in a different population, this set will represent a substantial gain for future use in clinical research.