Respiratory Tract Infections Due to Human Metapneumovirus in Immunocompromised Children

Chu, Helen Y.; Renaud, Christian; Ficken, Elle; Thomson, Blythe; Kuypers, Jane; Englund, Janet A.

Respiratory specimens were obtained by nasal washes for patients with suspected respiratory viral infections by attending physicians, or from bronchoalveolar lavage fluid (BAL) when this was performed. DFA was performed using virus-specific mouse monoclonal antibodies (Chemicon, Temecula, CA), and RT-qPCR was performed using previously published methods at the University of Washington Virology Laboratories [12] . Viral load values were obtained on a subset of patients whose samples were tested by RT-qPCR. Estimated viral load data were calculated from cycle threshold values on RT-qPCR analysis using stored standard curve data for hMPV. Upper respiratory tract infection (URTI) was defined as hMPV documented in an upper respiratory tract specimen in a patient with compatible symptoms in the absence of radiographic or clinical evidence of pneumonia. LRTI was defined as a new pulmonary infiltrate or presence of lower respiratory tract symptoms (wheezing or hypoxia) in association with a positive lower respiratory tract specimen or a positive upper respiratory tract specimen if the patient did not undergo BAL. Neutropenia was defined as absolute neutrophil count <1000 cells/mL. Lymphopenia was defined as lymphocyte count <300 cells/mL (not age-adjusted), and severe lymphopenia as lymphocyte count <100 cells/mL.