By: Dr. Geoffrey Modest
An Italian prospective study was just published looking at the merits of ultrasound in diagnosing pneumonia (see 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.