Chest XRay versus Chest CT for Diagnosis of Pneumonia
Date First Published:
December 18, 2015
Last Updated:
December 18, 2015
Report by:
Noah Hornick, Medical Student (Oregon Health & Science University)
Three-Part Question:
In [ED patients with suspected pneumonia], is [chest x-ray as sensitive as chest CT] for [supporting a diagnosis of pneumonia]?
Clinical Scenario:
A 28 year old male presents to the emergency department with a 2-week history of cough and progressive shortness of breath. An outside chest x-ray was non-diagnostic. Chest CT here demonstrates bilateral interstitial infiltrates, consistent with pneumonia. You wonder how often CT scan is necessary to diagnose a pneumonia after an equivocal chest x-ray.
Search Strategy:
In [ED patients with suspected pneumonia], is [chest x-ray as sensitive as chest CT] for [supporting a diagnosis of pneumonia]?
Search Details:
Medline 1996-present using the OVID interface.
[(exp pneumonia/ OR pneumonia.mp.) AND (chest xray or CXR).mp. AND (computed tomography or ct).mp.]
LIMIT to English language and humans
[(exp pneumonia/ OR pneumonia.mp.) AND (chest xray or CXR).mp. AND (computed tomography or ct).mp.]
LIMIT to English language and humans
Outcome:
Altogether 30 papers were identified, of which four were relevant to the question. Details are shown in table 1.
Relevant Paper(s):
| Study Title | Patient Group | Study type (level of evidence) | Outcomes | Key results | Study Weaknesses |
|---|---|---|---|---|---|
| False-negative chest radiographs in emergency department diagnosis of pneumonia. Maughan BC; Asselin N; Carey JL; Sucov A; Valente JH. Aug-14 USA | 428 ED patients from a single center admitted with a diagnosis of pneumonia | Retrospective cohort study | Percent of diagnoses made by chest x-ray vs chest CT | 11% of patients diagnosed by CT after negative / nondiagnostic chest x-ray | Single-center, retrospective design, not all CXR-diagnosed pts received CT |
| High discordance of chest x-ray and computed tomography for detection of pulmonary opacities in ED patients: implications for diagnosing pneumonia. Self WH; Courtney DM; McNaughton CD; Wunderink RG; Kline JA. Feb-13 USA | 3423 ED patients from 12 EDs who received both CXR and chest CT | Retrospective cohort study | Opacity, infiltrate, consolidation, pneumonia, or bronchopneumonia on radiology report | CXR sensitivity 43.5% CXR positive predictive value 26.9% | Retrospective study design, reliance on CT as gold standard |
| Impact of clinical data on chest radiography sensitivity in detecting pulmonary abnormalities in immunocompromised patients with suspected pneumonia. Cereser L; Zuiani C; Graziani G; Girometti R; Como G; Zaja F; Bazzocchi M. Mar-10 Italy | 64 immuno-compromised patients with clinically suspected pneumonia | Experimental study | Retrospective read of CXR as consistent with pneumonia | CXR sensitivity 39-58.5% without clinical information, 41.5-43.9% with. | Small number of patients, reads by two radiologists, limited patient population |
| Chest radiograph vs. computed tomography scan in the evaluation for pneumonia. Hayden GE; Wrenn KW. 2009 USA | 97 ED patients from a single center with a diagnosis of pneumonia who received both CXR and chest CT | Retrospective cohort study | Numbers of negative or non-diagnostic chest radiographs in the setting of diagnostic CT scans | 27% of patients diagnosed by CT after negative / nondiagnostic chest x-ray | Single-center, retrospective design |
Author Commentary:
All studies noted a higher sensitivity of CT compared to chest x-ray in the diagnosis of pneumonia. The largest retrospective study also analyzed false positive CXR findings and noted a very low positive predictive value. Of note, in the small single study investigating an immunocompromised patient population, there was no significant difference in the sensitivity of CXR with clinical context versus without. In total, while CXR may provide supporting data in the context of an elevated index of suspicion, its sensitivity and specificity are inadequate to be relied upon to rule in or out a diagnosis of pneumonia.
Bottom Line:
Computed tomography is more sensitive than chest x-ray for the diagnosis of pneumonia; a negative or nondiagnostic CXR in the context of a high clinical suspicion should not be used to rule out this diagnosis.
References:
- Maughan BC; Asselin N; Carey JL; Sucov A; Valente JH.. False-negative chest radiographs in emergency department diagnosis of pneumonia.
- Self WH; Courtney DM; McNaughton CD; Wunderink RG; Kline JA.. High discordance of chest x-ray and computed tomography for detection of pulmonary opacities in ED patients: implications for diagnosing pneumonia.
- Cereser L; Zuiani C; Graziani G; Girometti R; Como G; Zaja F; Bazzocchi M.. Impact of clinical data on chest radiography sensitivity in detecting pulmonary abnormalities in immunocompromised patients with suspected pneumonia.
- Hayden GE; Wrenn KW.. Chest radiograph vs. computed tomography scan in the evaluation for pneumonia.