Pulmonary imaging of pandemic influenza H1N1 infection: relationship between clinical presentation and disease burden on chest radiography and CT

Abstract

ABSTRACT. The potential for pulmonary involvement among patients presenting with novel swine-origin influenza A (H1N1) is high. To investigate the utility of chest imaging in this setting, we correlated clinical presentation with chest radiographic and CT findings in patients with proven H1N1 cases. Subjects included all patients presenting with laboratory-confirmed H1N1 between 1 May and 10 September 2009 to one of three urban hospitals. Clinical information was gathered retrospectively, including symptoms, possible risk factors, treatment and hospital survival. Imaging studies were re-read for study purposes, and CXR findings compared with CT scans when available. During the study period, 157 patients presented with subsequently proven H1N1 infection. Hospital admission was necessary for 94 (60%) patients, 16 (10%) were admitted to intensive care and 6 (4%) died. An initial CXR, carried out for 123 (78%) patients, was abnormal in only 40 (33%) cases. Factors associated with increased likelihood for radiographic lung abnormalities were dyspnoea (p,0.001), hypoxaemia (p,0.001) and diabetes mellitus (p50.023). Chest CT was performed in 21 patients, and 19 (90%) showed consolidation, ground-glass opacity, nodules or a combination of these findings. 4 of 21 patients had negative CXR and positive CT. Compared with CT, plain CXR was less sensitive in detecting H1N1 pulmonary disease among immunocompromised hosts than in other patients (p50.0072). A normal CXR is common among patients presenting to the hospital for H1N1-related symptoms without evidence of respiratory difficulties. The CXR may significantly underestimate lung involvement in the setting of immunosuppression.

2009 pandemic Influenza A (H1N1): clinical and laboratory characteristics in pediatric and adult patients and in patients with pulmonary involvement

“…Lung consolidation and infiltrates with or without pleural effusion were the two plain film patterns found in chest radiographies in our patients. The possibility of an under‐diagnosis of pulmonary embolism and pneumo‐mediastinum that had previously been observed in patients with pandemic influenza A (H1N1) could not be excluded, 36 as our patients were evaluated by plain chest radiographs which were less sensitive in the detection of such abnormalities than a computed tomography 37 …”

Clinical Characteristics and Radiological Manifestations in Influenza a and (H1n1) Swine Flu Infection: Our Experience

“…L ABBO et al reported findings of bilateral infiltrate in patients with primary influenza viral pneumonia. 18 Some of the patients progressed from influenza symptoms to pneumonia, manifested by bilateral consolidation findings on chest radiograph consistent with the acute respiratory distress syndrome requiring mechanical ventilation. Thus in contrast to seasonal influenza A which runs a self-limited course, most of the serious illness are caused by H1N1 (swine flu)virus.…”

Pulmonary Manifestation of Novel Swine-Origin Influenza A (H1N1) Virus (S-OIV) Infection in Immunocompromised Patients: Initial Findings with Multidetector Computed Tomography

“…Recent reports demonstrated that immunocompromised individuals such as patients following hematopoietic stem cell transplantation and those receiving chemotherapy due to leukemia are at an increased risk for influenza and a more severe and prolonged course [7,8]. …”

“…So far, only little is known about the imaging findings in immunocompromised patients suffering from respiratory affection of S-OIV [8,9]. Therefore, the purpose of this study was to describe the initial pulmonary multidetector computed tomographic (MDCT) findings of S-OIV infection in immunocompromised patients and to determine whether or not identification of certain abnormalities can help predict patients who are at risk for a severe clinical course.…”