Evaluation of disease severity in familial Mediterranean fever

OBJECTIVE To establish a new, objective, statistically based severity score for familial Mediterranean fever (FMF). METHODS One hundred consecutive FMF patients were evaluated independently by 2 FMF experts for severity of their disease and were assigned to 1 of 3 severity levels: mild, intermediate, or severe. Nine candidate criteria, reflecting objective suffering and disability, were analyzed to determine their weight for patient placement in the 3 predefined severity groups. RESULTS Candidate criteria best differentiating between the 3 patient categories were the frequency of attacks, the number of sites affected during an attack and during the course of the disease, and the duration of the attacks. These criteria were applied in a classification-tree model to establish a new FMF-severity score (F-SS). The first set of F-SS (F-SS-1) was highly sensitive and specific. Integrating F-SS-1 with clinical parameters strongly associated with disease severity resulted in a simplified score, the second set of F-SS (F-SS-2). CONCLUSIONS New, useful, objective, and valid severity scores were established and found to distinguish between patients with mild, intermediate, and severe diseases with high sensitivity and specificity. RELEVANCE The F-SS established may be important for treatment decisions, prognosis evaluation, and comparative analysis of patient populations.