What is the sensitivity and specificity of upright chest x-ray (Chest Radiograph) in detecting focal pneumonia?

From the Guidelines

The sensitivity and specificity of upright chest x-ray in detecting focal pneumonia are 58% and 91%, respectively, as reported in the most recent study by Capp et al 1. This means that chest x-rays miss about 42% of pneumonia cases but rarely give false positive results.

Key Points to Consider

• The study by Capp et al 1 evaluated the accuracy of chest radiography in the diagnosis of pneumonia in ED patients admitted to the ICU with severe sepsis or septic shock.
• The sensitivity of 58% (95% CI, 46%-68%) indicates that chest x-rays may not detect pneumonia in a significant proportion of patients.
• The specificity of 91% (95% CI, 81%-95%) suggests that chest x-rays are reliable in ruling out pneumonia when the result is negative.

Clinical Implications

• Chest x-rays remain a valuable initial screening tool for pneumonia due to their portability, rapid acquisition, and potential to provide valuable information, especially in patients with sepsis who may not be able to provide a history.
• However, clinicians should be aware of the limitations of chest x-rays and consider additional imaging, such as CT scans, if clinical suspicion for pneumonia is high despite a negative chest x-ray.
• Patient positioning is crucial, and upright films are preferred over supine films to avoid missing infiltrates in dependent lung regions.

From the Research

Sensitivity and Specificity of Upright Chest X-ray

• The sensitivity of upright chest x-ray in detecting focal pneumonia is reported to be 67% (95% CI 56.4% to 76.9%) 2 and 69% 2 in two different studies.
• The specificity of upright chest x-ray in detecting focal pneumonia is reported to be 85% (95% CI 73.3% to 95.9%) 2 and between 80% and 90% 3 in two different studies.

Comparison with Other Imaging Techniques

• Compared to lung ultrasound, chest x-ray has lower sensitivity (67% vs 98%) and specificity (85% vs 95%) 2.
• Computed tomography (CT) scans have higher sensitivity (above 95%) and specificity (between 80% and 90%) compared to chest x-ray 3.
• Lung ultrasound is a reliable tool for diagnosing pneumonia, with a pooled sensitivity of 0.85 (0.84-0.87) and specificity of 0.93 (0.92-0.95) 4.

Limitations of Chest X-ray

• Chest x-ray lacks sensitivity and is less useful in diagnosing early disease 3.
• The interpretation of chest radiographs has been shown to have a lack of agreement, bringing their role as the ultimate arbiter of diagnosis into question 5.