Primary Predictor and Outcome Measures
The primary predictor was diagnosis of any type of ARI at the time of
respiratory culture collection, as defined using International
Classification of Diseases, Ninth Revision (ICD-9) and Tenth
Revision (ICD-10) diagnostic codes placed by clinicians during the
encounter in which the respiratory culture was obtained. Diagnostic
codes consistent with conservatively-defined acute bacterial, viral, or
nonspecific infection of the trachea or lower respiratory tract (e.g.,
pneumonia, tracheitis, ventilator-associated pneumonia; Appendix
Table 1 ) were identified from review of the Clinical Classification
Software-Respiratory Group diagnoses (Agency for Healthcare Research and
Quality, Rockville, MD) and selected by group consensus between authors.
A secondary predictor was evaluated for the subgroup of children with
bacterial-specific ARI diagnoses (bARI) at the time of respiratory
culture collection. bARI was defined using previously-identified ICD-9
codes12 and corresponding ICD-10 codes (e.g.,
bacterial pneumonia, acute bronchitis due to Streptococcus , acute
tracheitis; Appendix Table 2 ).
The primary outcome was respiratory culture organism isolation (any
isolation and specific organism isolation) in the first respiratory
culture obtained in each encounter. Cultures with no speciated organisms
or identification of only “oropharyngeal flora” were categorized as
“negative”. The CCHMC Microbiology Laboratory performs
semi-quantification of species for TA cultures and full quantification
for BAL cultures. The Microbiology Lab does not have specimen rejection
criteria. The Lab defines oropharyngeal flora broadly, and categorizes
such species as Haemophilus , S. pneumoniae , and M.
catarrhalis as oropharyngeal flora when isolated in small numbers in
the presence of other oropharyngeal flora (Appendix Figure 1 ).