Background: Dengue fever is a major public health issue forming a burden of monsoon related illness. There is a need to study the clinical features and laboratory investigations to predict the severity of dengue fever for timely intervention and management to decrease the morbidity and mortality. Methods: An observational prospective study was conducted in children of less than 12 years of age in hospitalised cases, to study the severity of clinical features and variations in laboratory finding in proved cases of dengue fever. All cases of thrombocytopenia were included in this study and proved cases of dengue fever which were positive for NS1 antigen (done by ELISA using Dengue NS1 Ag microlisa kit) or IgM antibodies to dengue (done by using DEN MAC ELISA kit) or both NS1Ag and IgM antibodies were compared with laboratory finding of other causes of thrombocytopenia. Results: This study encountered 130 patients with thrombocytopenia during the period of 18 months. Of these 114 cases had infective cause, 12 cases had haematological cause and 4 cases of nutritional deficiency as etiology. Of the 114 cases of infective cause, 47 cases were proved dengue fever. Out of the 47 cases of dengue fever, 22 cases were positive for NS-1 antigen, 14 cases were positive for IgM antibody and 11 cases were positive for both antigen and antibody. Bleeding manifestations were found in 42.55% of cases. In severe thrombocytopenia cases more than three fourth cases had bleeding manifestations. Mortality for dengue was seen in 4.25% of cases. All the patients who expired belonged to Dengue Shock Syndrome. Conclusion: A significant association was seen between bleeding manifestations and severity of thrombocytopenia. A statistically significant correlation of p value < 0.001 was seen with relation to platelet count of dengue and non dengue viral infections.

Keywords: Dengue Fever; NS-1 Antigen; Thrombocytopenia.