Adult-onset Still's disease: still a diagnosis of exclusion. A nested case-control study in patients with fever of unknown origin.

Objectives: Several sets of criteria have been proposed to classify adult-onset Still's disease (AOSD), those of Yamaguchi being the most commonly used. The Yamaguchi criteria demand the exclusion of other conditions. A clinical scale, recently proposed by Crispin et al., but not yet validated, would allow a positive diagnosis of AOSD in a majority of patients, without the need of thorough diagnostic procedures.

Methods: From a database of 447 patients with classical fever of unknown origin (FUO), collected over a 10-year period (2000-2009) at a general internal medicine department of a university hospital, 22 patients with AOSD according to the Yamaguchi criteria were extracted and compared with 44 controls, matched to index year. Clinical and laboratory parameters were recorded. Sensitivity, specificity and accuracy of the Yamaguchi criteria and of the clinical score were assessed.

Results: Lower age, joint symptoms, rash, throat ache, neutrophilic leukocytosis, and elevated erythrocyte sedimentation rate were the principal characteristics supporting a diagnosis of AOSD in patients with FUO. Sensitivity, specificity, and accuracy of the Yamaguchi criteria were 95% or more. The clinical scale, while being specific (98%), lacked sensitivity (55%) and had lower accuracy (83%).

Conclusions: In patients with FUO, the Yamaguchi criteria are a time honored and reliable guide to a diagnosis of AOSD. The clinical scale may serve to rule in, rather than to rule out, AOSD. In many patients, Still's disease is still a diagnosis of exclusion.