Putative invasive pulmonary aspergillosis in apparently immunocompetent patients within medical wards and intensive care units

Abstract

Despite advances in evaluation and tests, patients in the ICU may have a suspected infection without a specific microbiological diagnosis. Candida and Aspergillus infections are the most frequent fungal infections in ICU patients, and aspergillosis carries a high mortality. Invasive pulmonary aspergillosis (IPA) is recognized as a cause of pneumonia in immunocompromised patients, and EORTC/MSG guidelines provide diagnostic criteria based on biopsy or culture from a sterile site, or (1) lower respiratory tract specimen (2) galactomannan antigen in plasma and/or alveolar lavage fluid, and other clinical features [1]. In contrast, for patients who are not immune compromised, there is a lack of specific diagnostic testing for IPA [2]. Critically ill patients, especially those with sepsis, may be relatively immune suppressed even if they do not have a primary diagnosis traditionally associated with immune compromise. Sepsis can cause immune suppression characterized by lymphopenia with increased susceptibility to secondary infection and mortality [3]. Typically, these patients cannot tolerate a lung biopsy or invasive tests to achieve a diagnosis of proven IPA [2]. Furthermore, even the terms “probable” or “possible” invasive pulmonary aspergillosis were developed for classical immune-compromised hosts and may not be applicable to the ICU patient [1]. However, given the case fatality rate of over 50% associated with IPA, it is important to have tools to establish a diagnosis [4]. An alternate diagnostic algorithm for IPA in the nonimmune-compromised critically ill patient who may not fit EORTC/MSG criteria was evaluated by Blot and colleagues in 2012. This clinical algorithm, studied in 524 critically ill patients, made use of the EORTC/MSG criteria for proven invasive pulmonary aspergillosis, and added a category termed putative invasive pulmonary aspergillosis (PIPA), which first requires a positive lower respiratory tract culture and incorporates additional clinical and host criteria. Under these guidelines, patients who did not fit into either the proven or putative category were defined as being colonized. When compared with histopathology-controlled patients, this algorithm was found to be 92% sensitive and 61% specific [2]. In this issue of IAEM, Corcione and colleagues [5] used these same criteria for PIPA [2] to perform a retrospective observational single-center study of all hospitalized patients with a positive Aspergillus culture from a lower airway sample obtained via bronchoalveolar lavage (BAL) or bronchial aspirate (BA). The authors applied the defined clinical, host, and imaging criteria to establish a diagnosis of PIPA. Those patients who did not meet criteria were classified as colonized. Of the more than 80,000 patients presenting during a 4-year period, 76 had a positive lower respiratory tract culture, of whom 52 met criteria for a diagnosis of PIPA (68%) and the remaining 24 were said to be colonized. The predominant Aspergillus species was A. fumigatus in 73% of isolates. The analysis included patients on the medical wards and in the ICU. Of the 58 ICU patients in this study, 36 met the criteria for PIPA. Aspergillus positive lower airway culture results occurred at a rate of 4.94 per thousand patients in ICU and 0.28 per thousand patients in the medical wards. The authors add to the medical literature by reporting a rate for medical ward patients, and their results are similar to reported rates for ICU patients. Some in the study population were immune compromised as defined by EORTC/MSG. For instance, 16 patients were on immune-suppressive medication. Chronic diseases such as cardiovascular, obstructive airways, and malignancy were frequent in the population. ICU patients had sepsis, required supportive therapies, and the majority had abdominal or trauma surgery. A multivariate analysis found a high odds * Mark Alan Tidswell [email protected]