Improving diagnostic accuracy for invasive pulmonary aspergillosis in the intensive care unit

Aspergillus spp is a widespread saprofytic fungus, frequently affecting the respiratory system and leading to variable clinical syndromes. Invasive pulmonary aspergillosis (IPA) is a well known life-threatening infection in patients with prolonged neutropenia, hematological malignancy, bone marrow or solid organ transplantation (1). Because of the difficult diagnosis of Aspergillus spp infections the European Organization for the Research and Treatment of Cancer/Mycoses Study Group (EORTC/MSG) has introduced a diagnostic algorithm that incorporates clinical, laboratory findings and risk factors for the stratification of patients into proven, probable or possible IPA (2). From the other side the incidence of IPA in critically ill patients is growing and has serious effects on survival (3). Although classic immunosuppression related to severe neutropenia or hematological malignancies is rather infrequent in the intensive care unit (ICU), other host risk factors have been recognized. Prolonged steroid treatment and comorbidities such as chronic obstructive pulmonary disease (COPD), diabetes, liver cirrhosis or end-stage chronic renal disease may occur in up to 50% of cases (4,5). In this group of patients the isolation of Aspergillus spp from the respiratory tract is difficult to be interpreted as IPA because of the lack of a diagnostic tool able to discriminate colonization from infection (except biopsy) and because IPA is usually associated with non-specific clinical signs and symptoms and atypical radiological findings (6). The above mentioned EORTC/MSG diagnostic criteria are validated only in immunosuppressed patients and probably lead to underdiagnosis and undertreatment in the ICU setting (7,8).