Proposal for a simple algorithm to differentiate adult-onset Still's disease with other fever of unknown origin...

To identify several clinical and/or laboratory parameters which can differentiate adult-onset Still's disease (AOSD) from other causes of fever of unknown origin (FUO) and create a clinician-friendly algorithm for this purpose.

FUO patients hospitalized between March 2015 and September 2017 were recruited prospectively. AOSD patients diagnosed between 2001 and 2017 in our department were analyzed. Clinical and laboratory parameters were recorded for all patients. A multivariate analysis was performed to identify possible parameters related to the discrimination of AOSD from FUO.

We recruited 69 AOSD patients (51 females, 74%) and 87 patients (43 females, 49.4%) evaluated for FUO. Median ages were 45 (30-57) and 45 (30-62), respectively. Arthralgia, rash, sore throat, neutrophilia, serum ferritin level higher than 5 times of the upper limit, and elevated lactate dehydrogenase levels were associated with the likelihood of diagnosing AOSD; on the other hand, the number of daily fever peaks equal or greater than 3 was associated with the unlikelihood of diagnosing AOSD. After the clinical feasibility assessment of possible parameters derived from the multivariate analysis, in the setting of fever, two clinical (arthralgia, sore throat) and two laboratory (ferritin level, neutrophilia) parameters were selected to develop an algorithm for discrimination of AOSD and FUO.

Presence of arthralgia, hyperferritinemia, sore throat, and neutrophilia suggests AOSD in patients presenting as FUO. This study proposes a clinician-friendly algorithm for the first time in current literature to discriminate AOSD from other causes of FUO.