LUS in the diagnosis and follow-up of CAP

Lung ultrasound (LUS) signs of pneumonia included subpleural lung consolidation, B-lines, pleural line abnormalities, and pleural effusion.

July 12, 2012 -- NEW YORK (Reuters Health) - Lung ultrasound (LUS) is useful for diagnosing and following up community-acquired pneumonia (CAP), according to a new report.

"LUS offers several different applications, especially if chest x-ray is not available (in point-of-care ultrasonography, in emergency units, in a general practitioner practice) or not applicable," said Dr. Angela Reissig, whose findings were published online June 14 in Chest.

"In cases with sonographic evidence of pneumonia, the diagnosis can be established and the therapy can start immediately," Dr. Reissig, from Friedrich-Schiller-University Jena in Germany, told Reuters Health by email.

She and her colleagues sought to determine the accuracy of LUS in diagnosing CAP compared with two-plane chest x-ray and, when x-ray was negative or equivocal, with low-dose CT.

The study population included 362 patients with clinically suspected CAP who underwent LUS and chest x-ray. Sixty-three patients underwent low-dose CT.

LUS correctly diagnosed CAP in 211 of 226 patients with confirmed CAP, for a sensitivity of 93.4%. Sonographic signs of pneumonia were lacking in 127 of 130 patients without CAP, for a specificity of 97.7%.

Chest x-ray alone was slightly less sensitive (199/215, 92.6%) and slightly more specific (122/122, 100%) than LUS for diagnosing CAP.

Twenty-six cases of LUS-detected CAP were missed or equivocal by x-ray, whereas 14 cases of x-ray-detected CAP were missed by LUS.

Sonography also proved useful for documenting disease remission, and results of follow-up LUS were concordant with follow-up x-rays in 85 (75.6%) patients.

"About 8% of pneumonic lesions are not detectable by LUS," the researchers write. "Therefore, an inconspicuous LUS does not exclude pneumonia."

"We have shown that it is possible to diagnose and follow-up CAP by LUS with a very good sensitivity and specificity (at least comparable with chest x-ray in two planes)," Dr. Reissig concluded.

By Will Boggs, MD

Abstract

Background: The aim of this prospective multicentre study was to define accuracy of lung ultrasound (LUS) in diagnosing community-acquired pneumonia (CAP).

Methods: 362 patients with suspected CAP were enrolled in 14 European centres. At baseline, history, clinical examination, laboratory testing and LUS were performed as well as the reference test: X-ray in two planes or low-dose CT in case of inconclusive/negative X-ray but positive LUS. In patients with CAP, follow-up between day 5-8 and 13-16 was scheduled.

Results: CAP was confirmed in 229 patients (63.3%). LUS revealed a sensitivity of 93.4% with 95% confidence interval of [89.2%,96.3%], a specificity of 97.7% [93.4%,99.6%], and likelihood ratios (LR) of 40.5 [13.2,123.9] for positive and 0.07 [0.04,0.11] for negative results. A combination of auscultation and LUS increased positive LR ratio to 42.9 [10.8,170.0] and decreased negative LR to 0.04 [0.02,0.09].97.6% (205/210) of patients with CAP showed breath-dependant motion of infiltrates, 86.7% (183/211) an air bronchogram, 76.5% (156/204) blurred margins, 54.4% (105/193) a basal pleural effusion. During follow-up, median C-reactive protein decreased from 137 to 6.3 mg/dl at day 13-16 as well as signs of CAP: median area of lesions decreased from 15.3 to 0.2 cm2, pleural effusion from 50 to 0 ml.

Conclusions: LUS is a non-invasive, usually available tool for diagnosing CAP with high accuracy. This is especially important if X-ray is not available or not applicable. About 8% of pneumonic lesions are not detectable by LUS. Therefore, an inconspicuous LUS does not exclude pneumonia.

ClinicalTrials.gov Identifier: NCT00808457
Source: http://bit.ly/P1kmny