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 <0.2). Hypotensive shock was the exception for both classifications, presenting dependence (Z = 56.42; P < 0.001, and Z = 55.24; P < 0.001) and high agreement (Cramers's V = 1; P < 0.001, and Cramers's V = 0.97; P < 0.001) for WHO 1997 and 2009, respectively. Last, we also found substantial agreement in disease classification between both guidelines (Kendall tau‐b = 0.79; P < 0.001), although 2009 guidelines were more sensitive in the detection of severe cases. Conclusions We hope our results will inform the debate about dengue classification guidelines, particularly concerning clinical value, study comparability, and ways in which future guidelines can support the clinical management of dengue. Our results suggest that caution should be taken when using WHO guidelines to assess dengue severity to improve clinical management of patients.

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Background We evaluated the validity of clinical diagnosis compared with laboratory diagnosis of dengue in a retrospective sample of patients in São José do Rio Preto, Brazil. Methods Our sample included 148 299 clinically (56.3%) or laboratory-diagnosed (43.7%) dengue cases. We compared the sensitivity, specificity, positive and negative predictive value (PPV and NPV) of dengue patients’ demographic and clinical characteristics with laboratory-based diagnosis. We used logistic regressions to estimate the correlation between clinical and laboratory diagnosis of dengue and a full set of dengue signs and symptoms. Results We found substantial variability in sensitivity and specificity of signs and symptoms ranging from 0.8–81.1 and 21.5–99.6, respectively. Thrombocytopenia exhibited the highest PPV (92.0) and lowest NPV (42.2) and was the only symptom showing agreement with laboratory-confirmed dengue (φ = 0.38). The presence of exanthema and thrombocytopenia led to a greater likelihood of concordant clinical and laboratory diagnoses (exanthema: OR: 4.23; 95% CI: 2.09 to 8.57; thrombocytopenia: OR: 4.02; 95% CI: 1.32 to 12.27). Conclusions We found substantial variation in sensitivity, specificity, PPV and NPV of dengue signs and symptoms. For accuracy, clinical and laboratory diagnosis of dengue should be performed concurrently. When laboratory tests are not available, we suggest focusing on the clinical manifestations most associated with dengue.

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