Lactate dehydrogenase and caspase activity in nasopharyngeal secretions are predictors of bronchiolitis severity

Mehta, Reena; Scheffler, Margaret; Tapia, Lorena; Aideyan, Letisha; Patel, Kirtida D; Jewell, Alan M; Avadhanula, Vasanthi; Mei, Minghua; Garofalo, Roberto P; Piedra, Pedro A

A single NPA sample was collected as previously described at enrollment, either in the emergency department or within 24 hours of admission to the ICU. 14,15 NPA was used as a surrogate for the lower respiratory tract, as several studies confirm virus titers obtained in nasal washes correlate with disease activity in the lower airways. 16 Briefly, NPAs were collected by instilling 2 cc of normal saline into the external nares, then aspirating the material into a 5-cc syringe containing an additional 2 cc of normal saline via a flexible catheter. Samples were stabilized with viral transport media (Iscove media with 15% glycerol) in a 1:1 dilution and refrigerated at 4 degrees before being transported to the Respiratory Virus Diagnostic Laboratory (CLIA ID 45D0919666) at Baylor College of Medicine. At the laboratory, specimens were divided into six aliquots of 0Á5-1 cc and snap-frozen in an alcohol-dry ice bath and stored at À80°C. NPAs were generally processed within 24 hours of collection. Mucus presence in NPA specimens was evaluated weekly during enrollment by testing for the presence of secretory IgA (sIgA), a major immunoglobulin in mucosal defense, by a captured ELISA method using commercially available reagents ( 17, 18 ). Only five NPA samples from the enrolled children demonstrated inadequate sIgA levels; these subjects were not resampled.