Chest Imaging Studies Play Key Role in SARS Diagnosis

At least until definitive tests are available, chest radiographs (x-rays) and computed tomography (CT) scans will play a critical role in the diagnosis of severe acute respiratory syndrome (SARS), reports a study in the July issue of Journal of Thoracic Imaging.

Dr. Jeffrey Seow-Kuang Goh and colleagues of Tan Tock Seng Hospital, Singapore, detail the chest imaging results of one woman with SARS, a 28-year-old "domestic helper." She was helping to care for a patient in the hospital's intensive care unit, where a staff nurse was diagnosed with SARS.

The patient's initial symptoms included shortness of breath and fever, typical of early cases of SARS. Her first chest radiograph showed relatively mild, "patchy" abnormalities, consistent with atypical pneumonia. These types of x-ray changes are part of the World Health Organization's definition for "probable" cases of SARS.

As the patient's condition worsened, so did the appearance of her lungs on chest radiographs. A chest CT scan, performed to rule out possible causes other than SARS, showed additional details of the SARS-related changes in the patient's lungs that were not visible on conventional x-ray films. By the time the CT scan was performed, the patient's symptoms had gotten so bad that she was unable to hold her breath for the scan.

Over the next several days, she gradually recovered with basic medical care. Follow-up chest radiographs and CT scans showed gradual resolution of the SARS-related lung changes as well, despite some signs of scarring. The patient was well enough to leave the hospital three weeks after her first symptoms.

"SARS is the first severe and easily transmissible infectious disease outbreak of the new millennium," Dr. Goh and his coauthors write. Since the SARS outbreaks was first recognized, intensive medical investigation has identified a new type of coronavirus as the likely cause. However, current tests for coronavirus can take up to three weeks to show results.

Kits for quick, accurate diagnosis of SARS are under development. Until they are available, chest imaging studies will continue to play a key role in diagnosing SARS. The new report is one of the first to detail the changing radiographic findings of SARS, from initial patchy changes, to more severe involvement, to lung scarring as the condition resolves.

Chest CT scans may show evidence of SARS before x-rays do, the new report suggests. Dr. Goh and colleagues recommend CT scanning not only to promote early recognition of SARS, but also to monitor patients as they recover.

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