Original Contribution
Performance comparison of lung ultrasound and chest x-ray for the diagnosis of pneumonia in the ED

https://doi.org/10.1016/j.ajem.2013.10.003Get rights and content

Abstract

Objective

The aim of our study was to assess the potential of bedside lung ultrasound examination by the attending emergency physician in the diagnosis of acute pneumonia.

Material and Methods

This observational single-center study was conducted between January 2010 and June 2012 in the emergency unit of a general hospital, and analyzed 144 adult patients. The ultrasound examination was performed by one of five trained emergency physicians, and a chest radiograph interpreted by a radiologist. The primary end point was the diagnosis of hospital discharge.

Results

We found a sensitivity of 0.95 for the ultrasound examination against 0.6 for radiography (P < .05). The negative predictive value was 0.67 against 0.25 for radiography (P < .05).

Conclusion

These results exhort to promote the use of thoracic ultrasound in the first-line diagnosis of pneumonia.

Introduction

Acute pneumonia is the first cause of mortality related to infectious disease in Western countries, and on major cause of severe sepsis and septic shock [1]. However the diagnosis of acute pneumonia is often difficult in the emergency setting, as clinical, biological, and imaging sign are not specific [2].

International guidelines recommend the use of chest x-ray as first line examination, despite its low sensitivity and specificity [3]. Thoracic computed tomography (CT) scan, although considered as the gold standard, is often not performed and involves an important exposure to ionizing radiations, limiting its use to difficult cases.

Lung ultrasounds have shown a growing interest during the last few years in the diagnosis of pleural effusions, pneumothorax, pneumonias, or pulmonary contusions [4], [5], [6]. Most studies were realized in patients from intensive care setting. The results are so encouraging that in some units, chest x-rays have been replaced by lung ultrasounds in the follow-up of the patients [7], [8]. In the emergency department (ED), the use of lung ultrasounds in the diagnosis of acute pneumonia has been studied in only a few studies [9]. Because of the bedside use of the ultrasound units, result can be immediately available preventing any delay in the diagnosis process. Moreover, its realization by the attending emergency physician could allow a substantial time-saving for the establishment of the diagnosis and consequently reduce the length of stay at the ED. However, the reliability of ultrasound diagnosis of acute pneumonia by ED physician must be confirmed before generalization of its use.

The aim of this study was to assess the potential of bedside lung ultrasound examination by the attending emergency physician in the diagnosis of acute pneumonia.

Section snippets

Material and methods

The study protocol has been approved by the local Ethics Committee of our institution (PV 27613).

In this single-center study, patients were included in the ED setting if presented the following criteria:

Age 18 years and older, suspected of infectious acute pneumonia with at least three of the following items: tympanic temperature equal or higher than 38°C, cough, dyspnea, heart rate higher than 100 beats per minute, saturation of oxygen lower or equal to 92% in ambient air.

Five emergency

Statistical analysis

Continuous variables were expressed as means ± SD and categorical data as numbers (percentages). The performance of each examination was expressed as sensitivity, specificity, positive and negative predictive values, and then compared by χ2 test.

A value of P < .05 was considered as a statistical significance. A population size calculation has been performed based on a preliminary study performed in our units, and found the need to include at least 120 patients to allow detection of a difference

Results

One hundred sixty-six patients were included from January 2010 to June 2012. Twenty-two patients were secondarily excluded, resulting in 144 finally analyzed patients. (Fig. 3)

The study population included 72 men and 72 women aged 77.6 ± 15.2 years. The diagnosis of pneumonia was retained after hospitalization for 123 of them. The respective diagnosis performances of lung ultrasound and chest x-ray, and their comparison are shown in Table 1.

Nine patients who were diagnosed with pneumonia after

Discussion

The present study is one of the first to show a potential interest for the lung ultrasound compared to standard care patients for the diagnosis of acute pneumonia in non-selected ED patients. This study reveals a significantly higher sensitivity of lung ultrasound for the diagnosis of acute pneumonia compared to chest X-ray (95% vs 60%, P < .01). Interestingly lung ultrasound appears to be particularly more effective than chest X-ray when pneumonia is evolving for less than 24 hours. Moreover,

Conclusion

This study shows a clear superiority of lung ultrasound performed by a trained ED physician over the chest x-rays for the diagnosis of acute pneumonia. Given the ultrasonography performance for the diagnosis of acute pneumonia, lung ultrasound could replace chest x-ray as the first-line imaging investigation. In difficult cases (deep lesion) or in case of negative ultrasound, thoracic CT scan could be performed as suggested by a proposed decision-making algorithm for acute pneumonia diagnosis

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Conflict of interest: The authors have no conflict of interest to disclose.

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