Validation of a case definition for leptospirosis diagnosis in patients with acute severe febrile disease admitted in reference hospitals at the State of Pernambuco, Brazil

introduction: leptospirosis is often mistaken for other acute febrile illnesses because of its nonspecific presentation. bacteriologic, serologic, and molecular methods have several limitations for early diagnosis: technical complexity, low availability, low sensitivity in early disease, or high cost. this study aimed to validate a case definition, based on simple clinical and laboratory tests, that is intended for bedside diagnosis of leptospirosis among hospitalized patients. methods: adult patients, admitted to two reference hospitals in recife, brazil, with a febrile illness of less than 21 days and with a clinical suspicion of leptospirosis, were included to test a case definition comprising ten clinical and laboratory criteria. leptospirosis was confirmed or excluded by a composite reference standard (microscopic agglutination test, elisa, and blood culture). test properties were determined for each cutoff number of the criteria from the case definition. results: ninety seven patients were included; 75 had confirmed leptospirosis and 22 did not. mean number of criteria from the case definition that were fulfilled was 7.8±1.2 for confirmed leptospirosis and 5.9±1.5 for non-leptospirosis patients (p<0.0001). best sensitivity (85.3%) and specificity (68.2%) combination was found with a cutoff of 7 or more criteria, reaching positive and negative predictive values of 90.1% and 57.7%, respectively; accuracy was 81.4%. conclusions: the case definition, for a cutoff of at least 7 criteria, reached average sensitivity and specificity, but with a high positive predictive value. its simplicity and low cost make it useful for rapid bedside leptospirosis diagnosis in brazilian hospitalized patients with acute severe febrile disease.