Comparison between the traditional (1997) and revised (2009) WHO classifications of dengue disease: a retrospective study of 30 670 patients

OBJECTIVE To compare WHO's traditional (1997) and revised (2009) guidelines for dengue classification, using a large sample of patients of all ages with varying clinical conditions from a dengue-endemic area in Brazil. METHODS We compared 30 670 laboratory-confirmed dengue cases (1998-2012) using both WHO's dengue classification guidelines. Stereotype ordinal logistic regressions were used to analyse the association between patients' demographics and signs and symptoms related to dengue infection severity, as defined in the 1997 and 2009 guidelines. We then compared the degree of agreement in dengue classification of both guidelines. RESULTS Dengue signs and symptoms in patients were poorly correlated to disease severity as defined by both guidelines (Cramer's V test