lung ultrasound to diagnose pneumonia?

A​n Italian prospective study was just published looking at the merits of ultrasound in diagnosing pneumonia (see pneumonia dx ultrasound am j em med 2015 in dropbox, or Am J Emerg Med 2015 May; 33:620.). prior studies have found that chest xray (CXR) is not so sensitive, 43.5% in one study when compared to chest CT (which is considered the gold standard).  details:

--275 patients with respiratory complaints (60% dyspnea, 25% cough, 10% purulent sputum, 15% pleuritic chest pain) and underwent chest CT. mean age 71, 53.3% women. 
--Chest CT was positive for pneumonia (PNA) in 87 patients, with "almost perfect" concordance between the readings of 2 radiologists.
--lung ultrasound (LUS), done within 3 hours of the CT, and was positive in 81 patients. 72 of them (88.9%) also had a positive chest CT
    --the 9 false positives were: 3 lung cancer nodules, 3 cases of impaired ventilation not due to PNA, 3 cases of fibrotic bands
    --the 15 false negatives were: 3 cases of posterior consolidations (the LUS was only performed on anterior-lateral chest), 5 cases of deep infection without contact with the pleura
    ​--overall sensitivity was 82.8% (73.2-90%) and specificity was 95.5% (91.5-97.9%)
    --interobserver variability: "almost perfect"
    --in subgroup of patients with pleuritic chest pain: sensitivity was 91.7% and specificity was 97.4%
    --in subgroup wihtout pleuritic chest pain: sensitivity was 81.3% and specificity was 95% (other studies found LUS less reliable with deep-seated infections)
--CXR was done in addition to LUS in 190 patients:
    ​--sensitivity of LUS was 81.4% and of CXR was 64.3% (difference significant with p=0.036); specificities were similar (94.2% vs 90%)
--so, overall, LUS rules in consolidation well (+ likelihood ratio of 18.2), and is moderately good in ruling out consolidation ( - LR=0.18)

so, pretty inmpressive. this study confirms the relatively poor showing of CXR in diagnosing PNA, and found that LUS was really quite good, and the usual ultrasound concern of intra-observer variability was minimal. although this needs to be validated in other settings, this study does hold out the promise of a noninvasive and nonradiation-associated evaluation of pneumonia.

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