Detection of Familial Mediterranean Fever attacks by using a connected activity tracker and assessment of impact of attacks to daily physical activities: a pilot study Abstract Objective The objective of this study was to assess the impact of Familial Mediterranean Fever (FMF) attacks on daily physical activity and detect FMF attacks using a connected activity tracker. Methods Patients with FMF according to the Tel-Hashomer criteria were included in this prospective observational study. Attack-related data were collected weekly via phone call to avoid memory bias. Median steps in attack and attack-free days were calculated and compared using the Wilcoxon rank test. Sensitivity and specificity threshold for capturing attacks was set to two thirds of median steps per day in the whole observation period. Results Twelve patients participated in the study. The median age of patients was 26 (18–32) years, and 7 (58.3%) of them were male. Patients with attacks (n = 10) walked a median of 6990 (4552–11,531) steps per day in attack-free days, whereas this number decreased to a median of 1841 (590–4783) steps in attack days (p = 0.005). The activity tracker captured 42 of 45 attack days and 312 of 361 attack-free days. The cutoff value had 93% sensitivity and 86% specificity for capturing attacks. Conclusions FMF attacks significantly impair the physical activity of patients. Activity tracking may be a reasonable method to document FMF attacks. This might prevent errors due to memory bias and help accurately identify and treat patients with FMF.