Radiology: X-rays may help predict which H1N1 patients are at greatest risk

Chest radiograph of patient with H1N1 virus. Image Source: Radiology

Initial chest radiography may have significance in helping predict clinical outcome, but normal initial radiographs cannot exclude adverse outcome for patients with influenza A (H1N1), according to a study in the April issue of Radiology.

“Working in the emergency room is very stressful and physicians need information fast,” said lead author Galit Aviram, MD, head of cardiothoracic imaging in the department of radiology at Tel Aviv Sourasky Medical Center in Tel Aviv, Israel. “Our study provides significant findings that will help clinicians triage patients presenting with clinically suspected H1N1 influenza.”

Aviram and his colleagues retrospectively evaluated the chest x-rays of 97 consecutive patients with flu-like symptoms and laboratory-confirmed diagnosis of H1N1, admitted to the emergency department of Tel Aviv Sourasky Medical Center between May and September 2009. The researchers then correlated the x-ray findings with adverse patient outcomes. Major adverse outcome measures were mechanical ventilation and death.

The mean age of patients in the study, which included 53 men, was 40.4 years.

Sixty percent of 97 patients had normal radiographs; 3 percent of these had adverse outcomes, according to the authors. Characteristic imaging findings included the following: ground-glass (69 percent), consolidation (59 percent), frequently patchy (41 percent) and nodular (28 percent) opacities. Bilateral opacities were common (62 percent), with involvement of multiple lung zones (72 percent).

According to the researchers, findings in four or more zones and bilateral peripheral distribution occurred with significantly higher frequency in patients with adverse outcomes compared with patients with good outcomes (multi-zonal opacities: 60 vs. 6 percent; bilateral peripheral opacities: 60 vs. 15 percent).

“Abnormal findings in the periphery of both lungs and in multiple zones of the lungs were associated with poor clinical outcomes,” Aviram said.

Although a normal chest x-ray did not exclude the possibility of an adverse outcome, Aviram said the study’s findings can help physicians better identify high-risk H1N1 patients who require close monitoring.

“In H1N1, as in various types of community-acquired pneumonia, initial chest x-rays may not show abnormalities that develop later in the course of the disease,” Aviram concluded. “Further x-rays should be performed according to the patient’s clinical course.”