The objective of this study was to investigate the frequency of secondary thrombocytosis in children during RSV (respiratory syncytial virus) bronchiolitis and bronchiolitis caused by other cause. Predictive value of secondary thrombocytosis in relation with severity of clinical features and the outcome of the treatment in bronchiolitis affected children has also been studied.

In this retrospective study, medical records of 136 infants treated at Pediatrics department of County General Hospital Požega were used.

Demographic and other patients‘ features with bronchiolitis were collected from their medical records. The data was statistically examined.

The mean age of participants was 117,5 day. There were 72 (52,9%) boys and 64 (47,1%) girls. 94 (64,1%) of children had positive rapid antigen testing (immunoassay) for RSV from nasopharyngeal aspirate. Statistically significant association between duration of hospitalization and oxygen application in therapy, with thrombocytosis, was determined with logistic regression. The risk for thrombocytosis was increased with every day of hospitalization by 18,5%, and with the oxygen application in therapy by 33,1%. Need for hospitalization and development of pneumonia statistically do not have an influence on the development of thrombocytosis. There wasn’t statistically significant difference in trombocytosis according to RSV infection.

Children with bronchiolitis and thrombocytosis had a more severe course of the disease, which was presented with longer duration of hospitalization and the need for oxygen application in therapy.