Dengue fever in Brazilian adults and children:: assessment of clinical findings and their validity for diagnosis

Although it is well known that the signs and symptoms of dengue fever (DF) may overlap with those of other diseases, few attempts have been made to assess quantitatively their validity in the diagnosis of DF. The clinical data recorded, in the Brazilian town of Uberlandia between 1993 and 1998, on the notification forms from 495 serologically confirmed cases of DF and 650 patients who tested negative for this disease were therefore compared. Fever, headache, myalgia, retro-orbital pain and arthralgia were the most commonly reported symptoms among the confirmed cases (each occurring in at least 92% of the cases), whereas haemorrhagic manifestations (reported in 7% of cases) were uncommon. Although comparisons between the two groups gave risk ratios (RR) very close to 1 for most signs and symptoms, rash [RR = 1.86; 95% confidence interval (CI) = 1.63-2.13] and petechiae (RR = 1.38; CI - 1.07-1.79) were more commonly found among the confirmed cases. As the positive and negative predictive values of all of the signs and symptoms investigated were low, diagnosis of DF should not be based solely on clinical grounds.