A clinical guide for early detection of dengue fever and timing of investigations to detect patients likely to develop complications.

We aimed to identify clinical features that would be useful for case detection and the appropriate timing of investigations and hospital admissions in patients with short-duration fever, suspected to be dengue fever (DF). Of 928 adult patients with short-duration fever admitted to Colombo North Teaching Hospital, Sri Lanka during February-June 2004, one in four were randomly selected for assessment of the severity of six clinical features: headache, body aches, vomiting, retro-orbital pain, generalised weakness (scale 0-9) and skin erythema (grade 1-5). There were 148 DF patients (95 males, mean age+/-SD: 28+/-12 years) and 54 non-DF patients as controls (44 males, mean age+/-SD: 25+/-11 years). All symptoms assessed (cut-off >or=5) and skin erythema (>or=grade 2) had a good positive predictive value for DF. However, erythema had the best negative predictive value, helping to differentiate DF from other short-duration fevers. More than 95% of patients with dengue had a platelet count above 50000/microl until the third day of illness. The platelet counts were significantly reduced when erythema, fever, vomiting and generalised weakness were persistent. In conclusion, erythema elicited by hand impression may help in the prediction of DF, and follow-up blood counts are indicated when symptoms persist.