What are the findings of a chest X-ray (CXR) for pneumonia?

From the Guidelines

Chest X-ray (CXR) is a crucial diagnostic tool for pneumonia, and when pneumonia is suspected, a CXR should be obtained to confirm the diagnosis, assess severity, and guide treatment, as it can show infiltrates or consolidations in the lungs, with typical findings including lobar consolidation, interstitial patterns, or patchy infiltrates 1. The findings of a chest X-ray (CXR) for pneumonia can vary, but common features include:

• Lobar consolidation, which appears as a homogeneous area of increased opacity in one or more lobes of the lung
• Interstitial patterns, which can manifest as fine reticular or reticulonodular opacities
• Patchy infiltrates, which are scattered, patchy areas of increased opacity These radiographic findings can help distinguish between different types of pneumonia, such as bacterial, viral, or fungal, although clinical correlation is essential as imaging findings may overlap between different pathogens 1. In terms of diagnostic accuracy, a systematic review concluded that physician judgment alone frequently leads to overestimation of the probability of pneumonia, and that combinations of signs and symptoms can improve overall diagnostic accuracy, but even with the highest cutoff points for decision rules, the positive predictive value is rarely > 50% 1. The use of CXR in diagnosing pneumonia is supported by guidelines, which suggest that chest radiography should be performed if hypoxemia is documented or suspected, to identify the presence of a new infiltrate compatible with acute pneumonia and to exclude other complicating conditions 1. Overall, the CXR remains a valuable tool in the diagnosis and management of pneumonia, and its findings should be interpreted in the context of clinical symptoms and signs, as well as other diagnostic tests, to guide treatment and improve patient outcomes.

From the Research

Findings of Chest X-ray (CXR) for Pneumonia

• The diagnosis of pneumonia can be confirmed or excluded using a chest radiograph (x-ray) 2
• However, the interpretation of chest radiographs can be subjective and may not always be reliable, with several studies demonstrating a lack of agreement in the interpretation of chest radiographs 2
• A study found that the use of chest X-ray (CXR) when the physician is not sure of the diagnosis of pneumonia does not necessarily result in a lowered antibiotic prescribing rate 3
• In cases of negative findings on CXR, physicians may still prescribe antibiotics, suggesting that they do not fully rely on the outcome of the CXR 3
• Another study found that chest X-rays obtained in nursing homes may unnecessarily encourage antibiotic prescribing due to a high number of ambiguous or unclear readings 4
• The sensitivity of plain chest radiography in detection of pneumonia was found to be 82.85%, which is lower than that of ultrasonography (93.92%) 5
• Computed tomography (CT) scan can improve the diagnosis of pneumonia and reduce overdiagnosis, allowing for a better identification of alternative diagnoses 6

Diagnostic Accuracy of CXR

• The diagnostic accuracy of CXR can be limited by the quality of the image, the presence of chronic lung conditions, and the interpretation of the radiologist 4
• A study found that CXR had a false negative rate of 17.1% in detecting pneumonia, compared to ultrasonography which had a false negative rate of 6.1% 5
• The use of CXR as a diagnostic tool for pneumonia may need to be re-evaluated, particularly in cases where the diagnosis is uncertain or the patient has underlying lung disease 2, 3, 4

Alternative Imaging Strategies

• Ultrasonography and CT scan may be useful alternative imaging strategies for the diagnosis of pneumonia, particularly in cases where CXR is unclear or inconclusive 5, 6
• These imaging modalities may offer improved sensitivity and specificity compared to CXR, and can help to reduce overdiagnosis and inappropriate antibiotic use 5, 6