Risk of Subsequent Pneumonia After a Negative Chest Radiograph in the ED.

Background: Although chest radiograph (CXR) is frequently used to diagnose pneumonia, there is concern that radiographic findings may lag clinical findings, raising doubt around the reliance on CXR. This study sought to determine the percentage of children that develop radiographic pneumonia after an initially normal CXR, and to describe the characteristics of these patients.

Methods: This is a retrospective cohort study in a large tertiary pediatric emergency department (ED) over a 10-year period. Children younger than 21 years of age with suspected pneumonia whose initial CXR was negative and who underwent another CXR within 14 days were included in the study. Children with certain chronic medical conditions and those admitted to an intensive care unit were excluded.

Results: Among 9957 children with suspected pneumonia and a normal CXR in the ED, 240 underwent a follow-up CXR within 14 days, of whom 27 children (11% of children with a second CXR) had developed radiographic pneumonia. Tachypnea, hypoxemia, and dehydration were found to be predictors of radiographic pneumonia after an initially normal CXR.

Conclusions: The development of radiographic pneumonia following a normal CXR is rare in the ED setting. Clinicians can rely on the CXR to exclude a diagnosis of pneumonia in the ED setting but may exercise more caution in children with certain clinical features.