infectious diseases
Aspergillosis
Diagnosis of Aspergillosis
Usually fungal culture and histopathology of tissue samples Galactomannan antigen test on serum and/or bronchoalveolar lavage fluid species are common in the environment, positive sputum cultures may be due to environmental contamination or noninvasive colonization in patients with chronic lung disease; positive cultures are significant mainly when sputum is obtained from patients with increased susceptibility due to immunosuppression or neutropenia or when there is high suspicion due to typical imaging findings ( Diagnosis reference ). Conversely, sputum cultures from patients with aspergillomas or invasive pulmonary aspergillosis are often negative. Chest x-rays are taken; however, chest CT is far more sensitive and should be done if patients are at high risk (ie, neutropenic). CT of sinuses is done if sinus infection is suspected. A movable fungus ball within a cavitary lesion is characteristic on both, although most lesions are focal and solid. Sometimes imaging detects a halo sign (a hazy shadow surrounding a nodule) or cavitation within a necrotic lesion. Diffuse, generalized pulmonary infiltrates are seen in some patients. Culture and histopathology of a tissue sample are usually necessary for confirmation; histopathology helps distinguish invasive infection from colonization. The sample is typically taken from the lungs via bronchoscopy or percutaneous needle biopsy and from the sinuses via anterior rhinoscopy. Because cultures take time and histopathology results may be false-negative, most decisions to treat are based on strong presumptive clinical evidence. Blood cultures are almost always negative, even in rare cases of endocarditis. InAspergillusendocarditis, large vegetations often release sizable emboli that may occlude blood vessels and provide specimens for diagnosis. Echocardiograms, especially transesophageal echocardiograms, can show a mobile intracardiac mass consistent with a vegetation despite negative blood cultures. SerumAspergillusgalactomannan is specific but often not sufficiently sensitive to identify most cases in their early stages. In invasive pulmonary aspergillosis, the galactomannan test on bronchoalveolar lavage fluid is much more sensitive than that on serum and is often the only diagnostic option for patients with thrombocytopenia, for whom biopsy is contraindicated. Polymerase chain reaction (PCR) assays are available commercially. 1.Patterson TF, Thompson GR 3rd, Denning DW, et al: Practice guidelines for the diagnosis and management of aspergillosis: 2016 Update by the Infectious Diseases Society of America.Clin Infect Dis63(4):e1–e60, 2016. doi: 10.1093/cid/ciw326 