To determine the usefulness of serum ferritin and glycosylated ferritin (GF) levels in diagnosing adult onset Still's disease (AOSD).
We performed a retrospective multicenter study of 205 patients who had ferritin and GF assays in one hospital laboratory. Records of all patients were reviewed, and a standardized questionnaire used to extract all data available at the time of the assay. The clinicians' final diagnosis was also recorded. Patients were classified as having "certain AOSD" (based on Yamaguchi's criteria) or a control disease. The concordance of ferritin and GF levels with final diagnosis was evaluated.
In total 49 AOSD and 120 control patients were eligible. The mean ferritin value was significantly higher in the AOSD group (4,752 +/- 9,599 microg/l) than in the control group (1,571 +/- 3,807 microg/l), p = 0.029. GF was significantly lower in AOSD patients (15.9 +/- 11.9%) than in the control group (31.5 +/- 18.7%), p < 0.001. The combination of a GF level of < or = 20% with ferritin above the upper limit of normal yielded a sensitivity of 70.5% and specificity of 83.2%. The combination of a GF level < or = 20% with ferritin 5 times normal produced a sensitivity of 43.2% and specificity of 92.9%. This latter combination allowed an AOSD diagnosis to be ruled out for 6 of the 8 control patients who met Yamaguchi's positive criteria.
Ferritin and GF levels are powerful diagnostic markers of AOSD. They may be helpful in clinical practice for excluding differential diagnoses.