Bedside Lung Ultrasound as an Independent Tool to Diagnose Pneumonia in Comparison to Chest X-ray: An Observational Prospective Study from Intensive Care Units

Abstract

Background: Diagnosing pneumonia is challenging because of multiple differential diagnosis. Bedside lung ultrasound (BLUS) is a safe, portable, rapid and inexpensive new modality to diagnose pneumonia. This study was aimed to evaluate the sensitivity of BLUS vs chest X-ray (CXR) to diagnose community-acquired pneumonia (CAP) using computed tomography (CT) scans as the gold standard.

Patients and methods: An observational cross-sectional study was conducted in selected intensive care units (ICUs). Eligible 85 adult patients with symptoms suggestive of pneumonia as per 2007 Infectious Disease Society of America (IDSA), American Thoracic Society (ATS) criteria, and 2D echocardiography were enrolled consecutively by using convenient sampling technique. Real-time reverse transcription-polymerase chain reaction (RT-PCR) assay for SARS-associated coronavirus was sent with in 1 hour followed by BLUS and CXR within 24 hours of ICU admission. The final confirmation of CAP was done by a thoracic CT scan.

Results: Bedside lung ultrasound vs CXR could detect 74 vs 58 cases out of 84 confirmed cases. Sensitivity and specificity of BLUS vs CXR was 88.1% vs 67.8% and 100% vs 0%, respectively. Moreover, LR+ and LR- for BLUS was found to be 0 and 0.12 in comparison to 0.68 and 0 for CXR. The area under receiver operator characteristics (ROC) curve for BLUS vs CXR was 0.94 (95% CI 0.0-1.0) with p = 0.13 and 0.66 (95% CI 0.12-1.0) with p = 0.58. There was a significant agreement between diagnostic accuracy of BLUS and CT scan [kappa value (κ) = 0.14, p = 0.009], whereas CXR could not establish its diagnostic efficiency (κ = -0.023, p = 0.493). Sonographic features of pneumonia were B-lines, shred, and hepatization signs.

Conclusion: It is observed that BLUS showed higher sensitivity, specificity, and diagnostic accuracy as compared to CXR to diagnose pneumonia.

How to cite this article: Dhawan J, Singh G. Bedside Lung Ultrasound as an Independent Tool to Diagnose Pneumonia in Comparison to Chest X-ray: An Observational Prospective Study from Intensive Care Units. Indian J Crit Care Med 2022;26(8):920-929.

Keywords: Bedside lung ultrasound; Chest X-ray; Computed tomography scan; Diagnosis; Pneumonia.

Figs 1A and B

Sonosite used for the study

Figs 2A and D

Patterns suggestive of pneumonia. (A) Consolidation hypoechogenic area; (B) Shred sign fragmented pleural line; (C) B-lines; (D) Air-bronchogram pleural effusion

Flowchart 1

Diagrammatic representation of flow of study

Fig. 3

Frequency percentage of comorbidities present among patients (n = 85)

Fig. 4

Frequency distribution of patients’ RT-PCR report (n= 85)

Fig. 5

Frequency distribution of patients’ LVEF as calculated by 2D echocardiography (n = 85)

Fig. 6

Frequency percentage of patients’ regional wall motion abnormality represented by 2D echocardiography (n = 85)

Fig. 7

Frequency distribution of patients fulfilling major criteria for diagnosis of pneumonia (n = 85)

Fig. 8

Frequency distribution of patients fulfilling minor criteria for diagnosis of pneumonia

Fig. 9

Frequency distribution of detected number of pneumonia cases by BLUS and CXR in comparison to CT scan (n = 85)

Fig. 10

Positive and negative cases of pneumonia detected by BLUS (n= 85)

Fig. 11

Positive and negative cases of pneumonia detected by CXR (n = 85)

Fig. 12

The AUC for BLUS

Fig. 13

The AUC for CXR

Fig. 14

Represents BLUS findings

Fig. 15

The CXR findings

Fig. 16

The CT–chest findings