A recent meta-analysis published in Pediatrics reviews the diagnostic accuracy of lung ultrasound for pneumonia. According to the commentary, pneumonia is the leading cause of illness and death in children worldwide; it accounts for 18% of the total number of deaths in children <5 years, more than TB, AIDS, and malaria combined.

They performed a systematic search on several major databases using a combination of controlled keywords for age <18 years, pneumonia, and ultrasound. Of the initially 1475 identified studies, 8 were ultimately chosen for further evaluation.

Characterizing the meta-analysis:

- Three were conducted in the ED, 2 on the wards, 1 in the PICU and 2 in the NICU.

- Of the 765 children encompassed, the mean age was 5 years and they were 52% boys.

- Five of the 8 studies noted using highly skilled sonographers.

- The studies originated from Italy (5), US (1), China (1) and Egypt (1).

- All studies used CXR +/- clinical criteria as the diagnostic standard; LUS assessment was blinded to associated CXR results in 7 of 8 studies.

Results:

- LUS in the diagnosis of pediatric pneumonia had an overall pooled sensitivity of 96% (95% confidence interval [CI]: 94-97%) and specificity of 93% (95% CI: 90-96%).

- Positive and negative likelihood ratios were 15.3 (95% CI: 6.6-35.3) and 0.06 (95% CI: .03-0.11), respectively. For reference, remember that an LR >1 indicates an increased probability that the target disorder is present and >10 is a large or often conclusive increase in the likelihood of disease. Likewise, an LR <1 indicates a decreased probability that the target disorder is present and <0.1 is large or often conclusive decrease in the likelihood of disease.

- The area under the receiver operating characteristic (ROC) curve was 0.98. The ROC curve represents a measure of the accuracy of a test, >0.9 is considered to be excellent.

- In order to determine whether there are genuine differences underlying the results of the studies (heterogeneity) the I-squared statistic was implemented, with values consistent >0.45, demonstrating significant heterogeneity.

Bottom line: LUS appears to be an accurate test for the diagnosis of pneumonia in children. The limitation of this meta-analysis is mainly in the small number of studies and the significant heterogeneity between them, likely due at least in part to the fact that they used CXR +/- clinical data as the diagnostic standard. Nevertheless, the results provide evidence for the use of LUS as a cost-effective tool that potentially eliminates ionizing-radiation from the work-up of pediatric pneumonia and has application potential in resource-limited settings.

References