Dengue fever remains a major pediatric health challenge in tropical regions, with thrombocytopenia serving as a key marker of disease severity and bleeding risk. This prospective observational study evaluated the predictive value of mean platelet volume (MPV), the MPV-to-platelet ratio (MPV/PLT), and other complete blood count (CBC)-derived indices-including neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), and systemic immune-inflammation index (SII)-for severe thrombocytopenia in children with dengue. A total of 127 patients aged 1 month to 15 years with confirmed dengue (positive NS1 antigen and/or IgM) were enrolled at Hue Central Hospital, Vietnam, between January 2023 and July 2025. CBC parameters were measured on illness days 3 and 6, with severe thrombocytopenia defined as a platelet count below 50,000/µL on day 6. Severe thrombocytopenia developed in 15.7% of patients. The day-3 MPV/PLT ratio emerged as the strongest predictor (median 0.10 versus 0.05, p < 0.001), achieving an area under the ROC curve of 0.818, with 75.0% sensitivity and 88.8% specificity at an optimal cutoff of 0.0771. Elevated MPV, lower platelet counts, and reduced lymphocyte counts were also significantly associated with the outcome, while NLR showed only moderate discriminative ability and PLR and SII were not predictive. Multivariate analysis confirmed the independent contributions of lymphocyte count and MPV/PLT ratio. These findings indicate that the MPV/PLT ratio is a simple, inexpensive, and early laboratory marker that can help identify children at elevated risk of severe thrombocytopenia, supporting closer monitoring and more informed clinical decisions in pediatric dengue management.

Chau Duc Nguyen-Huu completed his PhD at the age of 34 years from Tokyo Medical and Dental University, Japan. He is an Associate Professor of Pediatrics at the University of Medicine and Pharmacy, Hue University, Vietnam, where he serves as Vice Director of the Institute for Training and Capacity Building of Health Personnel. He is also Vice Head of the Department of Pediatric Gastroenterology–Nutrition–Infectious Diseases at the Pediatric Center of Hue Central Hospital and an Executive Committee Member of the Vietnam Society of Pediatric Infectious Diseases. His research focuses on pediatric infectious diseases, sepsis, dengue, and hematological biomarkers. He has published multiple international papers in WoS/Scopus-indexed journals as first or corresponding author and has led several institutional and university-level research projects. He actively supervises residents, master’s students, and medical students and contributes to undergraduate and postgraduate teaching. In 2024 he was recognized as Associate Professor by the State Council for Professorship of Vietnam.