Data collection
This retrospective cohort study was conducted with the approval of the institutional review board at the Asan Medical Center,
and the requirement for informed consent was waived.
We searched the hospital database to identify all patients who had laboratory-confirmed HBoV infections between January 2010 and December 2017.
Patient characteristics including demographics,
smoking history,
underlying chronic disease,
body mass index,
immune status,
and features of HBoV infection,
which included seasonality,
type of infection (community acquired or nosocomial),
and presence of coinfection were thoroughly reviewed.
We also studied laboratory findings and clinical outcomes that included emergency room visits,
requirement for hospitalization,
intensive care unit admission,
and all-cause mortality rate (30 days,
90 days,
and overall mortality from the initial diagnosis of HBoV infection).
Definitions
Upper respiratory tract infection (URI) was defined as positive HBoV in the nasopharyngeal sample from patients with URI symptoms,
such as cough,
sputum,
and rhinorrhea.
Pneumonia was defined as the detection of HBoV in nasopharyngeal samples or BAL,
with initial or new pulmonary infiltrations on chest radiography or CT images.
Patients diagnosed with pneumonia two days after the initial URI diagnosis were considered to progress from
URI to pneumonia.
Community acquired infection was considered when patients developed acute respiratory symptoms while they were outside the hospital or within the first five days after admission.
Coinfection was defined as the detection of other potential respiratory pathogens in nasopharyngeal samples,
BAL,
sputum,
or blood cultures within 15 days before and after the HBoV infection.
Neutropenia was defined as an absolute neutrophil count <1000/mL,
and lymphopenia was defined as an absolute lymphocyte count <500/mL.
Analysis of CT findings
CT findings were reviewed in consensus by two chest radiologists (KHJ and LHN with 4 years of experience in chest imaging).
Patterns of parenchymal abnormalities were assessed for the presence of consolidation,
ground-glass opacity (GGO),
centrilobular nodules, macronodules,
interstitial thickening,
lymphadenopathy,
and pleural effusion.
CT patterns were defined based on the glossary of terms provided by the Fleishner Society.
With respect to extent of parenchymal abnormalities,
the total extent and the extent of each consolidation and GGO using a percent volumetric scale were assessed.
The total number of involved lobes was also evaluated.
The distribution of parenchymal abnormalities was evaluated for bilaterality,
axial (central,
peripheral,
random),
and longitudinal locations(upper,
lower,
random).
The inner two-thirds of the lung was defined as central and the outer third of the lung was defined as peripheral with respect to axial location.
The lesions above the hilum were regarded as upper and those below the hilum were regarded as lower with respect to longitudinal distribution.
The lesions that could not be determined according to the above definitions were considered to adopt random distributions.
All axial and coronal CT images were reviewed on the picture archiving and communication system using the lung(window width 1500 HU,
window level -700 HU) and mediastinal (window width 450Hounsfield unit [HU],
window level 50 HU) windows for reading.
Statistical Analysis
Clinical and CT findings of HBoV infections were compared for categorical variables using the chi-square test or the Fisher exact test and for continuous variables using the independent t-test.
Multivariable logistic regression was performed to identify cross-sectional associations 98 between each risk factor and pneumonia occurrences among all patients.
All variables with P values less than 0.1 in univariate analysis were entered into the multivariate analysis and the results are shown as odds ratios (OR) and 95% confidence intervals.
P-values less than 0.05 were considered to be significant.
All statistical calculations were performed using SPSS version 21.0 (SPSS Inc.,
Chicago,
IL).