LAUSR

Background Adult onset Still’s disease (AOSD) is a rare, auto-inflammatory disease that commonly presents as fever of unknown origin (FUO). As AOSD can cause complications as reactive lymphohistiocytosis that can be mortal, discriminating AOSD from FUO is important. Ferritin, an acute phase reactant, is commonly high in patients with AOSD as a part of systemic inflammation. Objectives To determine a cut-off value of ferritin that favours AOSD over FUO. Methods Data from patients who admitted to Hacettepe University Hospitals, inpatients sections of department of internal medicine with the complaint of FUO collected prospectively during 30 months. Patients with uncertain diagnosis after all diagnostic procedures excluded. AOSD patients followed at Hacettepe University department of rheumatology were included. Of AOSD patients whose initial test ferritin levels were not available also excluded. For determination of cut-off values, receiver operator curve (ROC) analysis were done for each predetermined value. Upper normal level in our laboratory for ferritin is 336 ng/ml. Results Total 150 patients (n=63, for AOSD; n=87, for FUO) were included. Median ferritin level was significantly higher in AOSD group [1705 (657–6417) ng/ml vs. 424 (141–1188) ng/ml, p<0001]. FUO group were also divided into three subgroups: rheumatologic (n=31, 35.6%), infectious (n=28, 32.2%) and malignant (n=28, 32.2%) causes. Median ferritin levels for these subgroups were 222 (104–1020), 527 (145–1057), 599 (166–2766) ng/ml, respectively. Area under curve (AUC) 95% confidence intervals, sensitivity and specificity for predetermined cut-off values are given in Table-1. ROC curve for all ferritin levels are given in Figure 1.Abstract AB1140 – Table 1 Cut/off value (ng/ml) Area under curve (AUC) Sensitivity,% Spesificity,% p value 95%, Confidence Interval (CI) >UNL 0,73 98 49 <0001 0,65–0,81 >3xUNL 0,66 64 68 0001 0,56–0,74 >5xUNL 0,67 52 82 <0001 0,58–0,74 >750 0,69 75 63 <0001 0,60–0,77 >1250 0,66 59 76 0001 0,57–0,75 >2500 0,66 43 85 0001 0,57–0,75 *UNL: Upper normal limit (for ferritin: 336 ng/ml) Figure-1: ROC analysis for each ferritin level (AUC 0,77%95 CI; 0.70–0.84, p<0.001) Conclusions For each cut-off values for ferritin, test performances were quite well to differentiate patients with AOSD from FUO. While ferritin levels higher than upper normal level have 98 percent sensitivity, ferritin levels higher than 5 times of upper normal level have 82 percent specificity. Large number of patients in each FUO subgroup is needed to determine ferritin test performance for each particular group of patients to differentiate from AOSD. Disclosure of Interest None declared