Haematologic profile and predictors of outcome in paediatric scrub typhus: A prospective observational study

Objectives: Scrub typhus (ST) is a re-emerging vector-borne disease causing acute febrile illness in the Asia Pacific regions, particularly in India. This study was conducted to explore the role of complete blood count analysis in predicting ST in children. Material and Methods: A prospective observational cohort study was conducted on 634 paediatric patients with ST, which was confirmed by an immunoglobulin M enzyme-linked immunosorbent assay. The demographic and clinical features were recorded, such as duration of fever, signs of generalised lymphadenopathy, presence/ absence of eschar and organ system involvement. A detailed haematological workup was done, which consisted of haemoglobin level, total leucocyte count, differential count, absolute counts and platelet count. The association between haematological and clinical parameters was determined using a t -test and Chi-square test. Results: The common haematological findings seen in children with ST were absolute monocytopenia (82.6%), anaemia (65.5%), absolute eosinopenia (47.1%), thrombocytopenia (44.7%) and leucocytosis (38.6%). The fever (100%) was the most common presentation and eschar (316, 49.8%) was the first most common sign, followed by generalised lymphadenopathy (293, 46.2%). Occurrence of severity, prolonged hospital stays and delayed fever defervescence in children with ST showed significant association with low Hb and increased absolute neutrophil count and neutrophil/lymphocyte ratio (N/L) >2. Conclusion: Anaemia, leucocytosis and thrombocytopenia can be used as haematology markers to predict ST in children presenting with undifferentiated febrile illness from rural endemic areas. These can also be early markers to predict delayed fever defervescence and severity. An N/L ratio can alert to the possibility of impending severity.