Risk factors for severe respiratory syncytial virus disease in children with cancer: The importance of lymphopenia and young age

OBJECTIVE. We sought to determine the epidemiologic features of respiratory syncytial virus infection in immunocompromised pediatric patients and to identify the risk factors for severe disease. METHODS. We designed a retrospective study examining the experience with respiratory syncytial virus infection in pediatric patients with underlying malignancies and hematopoietic stem cell transplant recipients seen between 1997 and 2005. Clinical and laboratory data were extracted from patient records, and independent predictors of disease severity were investigated. RESULTS. Fifty-eight patients met the study criteria. Twenty-three patients (40%) had underlying diagnoses of acute lymphoblastic leukemia, 11 (19%) had solid tumors, and 24 (41%) were hematopoietic stem cell transplant recipients, had acute myeloid leukemia, or had severe combined immunodeficiency syndrome. Seventeen patients (29%) were < 2 years of age. Overall, 16 patients (28%) developed lower respiratory tract infections. The frequency of lower respiratory tract infections was highest in patients with hematopoietic stem cell transplants, acute myeloid leukemia, or severe combined immunodeficiency syndrome (42%). Independent predictors of lower respiratory tract infections were profound lymphopenia, with absolute lymphocyte counts of < 100 cells per mm(3), and age of <= 2 years. Of all patients with lower respiratory tract infections, 31% died as a result of respiratory syncytial virus infection. The overall mortality rate was low (5 of 58 patients; 8.6%). All deaths occurred in patients with lower respiratory tract infections who were before or after hematopoietic stem cell transplants or were < 2 years of age and receiving treatment for acute myeloid leukemia. Neutropenia was not a predictor of respiratory syncytial virus lower respiratory tract infection or death. CONCLUSIONS. This study identified profound lymphopenia and young age as independent predictors of respiratory syncytial virus-related lower respiratory tract infections in immunocompromised children. No association between neutropenia and respiratory syncytial virus-related morbidity or death was found. These findings can guide interventions for respiratory syncytial virus infection in high risk hosts.