Justification: although current guidelines increasingly recommend the diagnosis of CAP based on clinical manifestations,1 radiologic tests can be useful in its diagnosis and management. Recent studies2 have assessed the use of LUS as an alternative to CXR to avoid exposure to radiation. This study contributes additional data on the use of LUS in children managed in emergency settings.
Scientific rigour and validity: the population and setting were well defined. Patients were selected based on the clinical suspicion of pneumonia, although the authors did not clearly specify the clinical criteria for suspicion, which may affect the generalisation of the results, given the high incidence of pneumonia observed in this sample. Since the study only included patients in whom there was a high suspicion of CAP (pre-test probability of 95.6%), it may have overestimated the Sen and Spe of LUS. In the study, the gold standard for the diagnosis of CAP was the judgment of an expert paediatrician based on CXR and clinical, laboratory and outcome variables that were poorly defined. It seems that the reviewer that made the initial interpretation of LUS examinations was blinded to the results of the CXR, but it is not clear whether the expert that made the definitive diagnosis of CAP was also blinded.
The diagnostic test procedures were well defined. All children underwent both imaging tests, which were interpreted independently. Lung ultrasonography was performed by an expert, so the results may not be generalisable to different circumstances.
Although this was not the case in the study, the authors warned of the possibility of failing to detect CAP with LUS in cases in which consolidation does not reach the pleural region; furthermore, the sample was small, and the authors did not calculate the minimum sample size needed to detect this effect.
Clinical relevance: lung ultrasonography performed similarly to CXR, with a Sen of 92.42% (95% confidence interval [95 CI], 88.2% to 99.7), a Spe of 100% (95 CI, 100 to 100) and good accuracy (area under the curve, 0.962). To correctly diagnose 100 children with CAP, it would be necessary to perform 106 ultrasound examinations (number needed to diagnose [NND], 1.06*), compared to 105 CXRs (NND, 1,05*).
Both tests have a high sensitivity and specificity. There was a strong agreement between the two tests, although the confidence interval was wide (kappa coefficient, 0.92; 95 IC, 0.75 to 1.08).
The findings of this study were similar to those of other studies conducted recently in different settings, in which LUS was performed by staff with different levels of expertise and the diagnosis of CAP was based in clinical and/or radiologic criteria in children3 as well as adults.4 The study under review found a higher specificity, since it only included patients in whom there was a high clinical suspicion, and one of the tests that was being evaluated (CXR) was used in making the definitive diagnosis.
Applicability to clinical practice: although the sample was small, the study suggests that in children assessed in emergency settings in whom there is a high suspicion of pneumonia, LUS performed by experienced providers performs comparably to CXR with the advantage of not exposing patients to radiation. Some aspects to consider are the availability of LUS, the time needed to perform it, and the variability of its findings when performed by less-experienced staff.
Conflicts of interest: the authors of the commentary have no conflicts of interest to declare.