Comparing Diagnostic Imaging for Community-Acquired Pneumonia

Adults hospitalized with community-acquired pneumonia (CAP) that is visualized on computed tomography (CT) scan but not on concurrent chest radiograph have similar pathogens, disease severity, and outcomes as patients who demonstrated signs of pneumonia on chest radiographs, according to a study published in Chest. 

Cameron P. Upchurch, MD, of the Vanderbilt University School of Medicine in Nashville, Tennessee, and colleagues argued that these findings support using the same management strategy for patients with CT-only pneumonia that is used in individuals with pneumonia shown on chest radiography.

In this multicenter prospective surveillance study of adults hospitalized with CAP, the investigators compared presenting clinical features, pathogens, and outcomes of patients receiving chest radiography only or chest radiography followed by CT imaging to confirm pneumonia.

Of 2251 patients, 2185 (97%) had pneumonia visualized on chest radiography, whereas 66 patients (3%) had pneumonia visualized on CT but not on concurrent chest radiography. Patients with CT-only pneumonia had a clinical profile that was similar to the profiles of those with chest radiograph-confirmed pneumonia, including comorbidities, vital signs, hospital length of stay, prevalence of viral (30% vs 26%, respectively) and bacterial (12% vs 14%, respectively) pathogens, intensive care unit admission (23% vs. 21%, respectively), use of mechanical ventilation (6% vs 5%, respectively), septic shock (5% vs 4%, respectively), and inpatient mortality (0% vs 2%, respectively).

However, the authors noted several differences that may be of clinical significance between the 2 patient populations. Obese patients were more likely to have CT-only pneumonia, possibly because of poorer chest radiography sensitivity associated with x-ray beam attenuation by adipose tissue. The CT-only pneumonia group also had lower serum procalcitonin levels and a higher prevalence of human rhinovirus. In addition, 2 patients with CT-only pneumonia and a serum procalcitonin concentration <0.25 ng/mL had pneumococcal infection, underscoring an important finding of this study — that the combination of chest radiography and procalcitonin determination does not identify all bacterial pneumonia.

Reference

Upchurch CP, Grijalva CG, Wunderink RG, et al. Community-acquired pneumonia visualized on CT scans but not chest radiographs. Chest. 2018;153(3):601-610.