The Impact of Indeterminate Pulmonary Findings in Chest CT Reports on Antibiotic Utilization

Purpose: Indeterminate pulmonary findings are commonly reported on chest CT scans with uncertain language. This study examines the impact of those findings on antibiotics utilization.

Methods/Materials: The study population comprised of a subset of emergency department patients who underwent chest CT during 2012-2022. Specific search terms were used to classify radiology reports into three groups: 1) negative, 2) indeterminate, and 3) positive for pneumonia. Reports and CT scans were then reviewed. Demographic, clinical symptoms, laboratory data, antibiotics administered within 24 hours of imaging, and imaging findings were collected. Multivariate logistic regression analysis was subsequently performed.

Results: Out of 1168 patients, 457, 386, and 325 had chest CT results that were negative, indeterminate, and positive for pneumonia, respectively. The Positive group had a higher WBC count (12.4) compared to the negative and indeterminate groups (9.2 and 9.6, respectively). Antibiotics were least likely to be administered in the Negative group (27%), compared to the Indeterminate (46%) and Positive (78%) groups. Multivariate logistic regression analysis showed that Indeterminate results had an odds ratio (OR) of 2.35 for antibiotics administration, compared to an OR of 9.49 for Positive results. Comparison of CT findings in the Indeterminate and Positive groups showed that antibiotics usage was significantly decreased when the extent of disease was minimal (OR=0.55, p< 0.01) and usage was increased when consolidations were present (OR=2.75, p< 0.01). Notably, antibiotics was administered in 71 (34%) patients in the Indeterminate group with minimal extent of lung involvement.

Conclusions: This study demonstrates the positive association between indeterminate CT findings for pneumonia and subsequent antibiotics utilization. Both a very limited extent of lung involvement and absence of consolidation are independently associated with decreased usage of antibiotics. Further studies are required to optimize antibiotics use when imaging features are not diagnostic for infectious pneumonia.