Diagnostic value of ferritin and glycosylated ferritin in adult onset Still's disease

Objective. To determine the usefulness of serum ferritin and glycosylated f erritin (GF) levels in diagnosing adult onset Still's disease (AOSD). Methods. We performed a retrospective multicenter study of 205 patients who had ferritin and GF assays in one hospital laboratory. Records of all pati ents were reviewed, and a standardized questionnaire used to extract all da ta 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. Results. In total 49 AOSD and 120 control patients were eligible. The mean ferritin value was significantly higher in the AOSD group (4752 +/- 9599 mu g/l) than in the control group (1571 +/- 3807 mug/l). p = 0.029. GF was sig nificantly lower in AOSD patients (15.9 +/- 11.9%) than in the control grou p (31.5 +/- 18.7%), p < 0.001. The combination of a GF level of <less than or equal to> 20% with ferritin above the upper limit of normal yielded a se nsitivity of 70.5% and specificity of 83.2%. The combination of a GF level less than or equal to 20% with ferritin 5 times normal produced a sensitivi ty of 43.2% and specificity of 92.9%. This latter combination allowed an AO SD diagnosis to be ruled out for 6 of the 8 control patients who met Yamagu chi's positive criteria. Conclusion. Ferritin and GF levels are powerful diagnostic markers of AOSD. They may be helpful in clinical practice for excluding differential diagno ses.