Introduction
Invasive fungal diseases (IFD) pose significant morbidity and mortality risks, particularly among immunocompromised patients, but they can also affect non-neutropenic, critically ill adults in the ICU who lack classical risk factors. This diverse patient population, which includes both medical and surgical cases with various comorbidities, has led to the development of multiple definitions of IFD that often cater to specific subgroups.
To address this issue, the Invasive Fungal Diseases in Adult Patients in ICU (FUNDICU) project aims to create standardized definitions for IFD in non-neutropenic ICU patients, enhancing the comparability of research across diverse populations. These definitions are intended for clinical research, not for direct clinical practice, and are meant to complement, rather than replace, existing guidelines from the European Organization for Research and Treatment of Cancer (EORTC) and the Mycoses Study Group Education and Research Consortium (MSGERC). The FUNDICU definitions do not apply to ICU patients with classical immunocompromising conditions defined by the EORTC/MSGERC.
Methods
The FUNDICU project protocol was developed by a multidisciplinary panel of experts from the European Society of Clinical Microbiology and Infectious Diseases (ESCMID) and other relevant organizations. The project involved systematic reviews to evaluate existing definitions and diagnostic tests for invasive fungal diseases (IFD) in non-neutropenic ICU patients, with literature searches updated until March 31, 2022.
Using the RAND/UCLA appropriateness method, panel members rated proposed definitions on a scale from 1 to 9 via REDCap software. Definitions were classified based on median scores, with two voting rounds necessary to evaluate initial and alternative definitions. Definitions rated as “appropriate” or “possibly considered” were further discussed in an online meeting, requiring at least 70% agreement for acceptance.
A fourth round of voting occurred after peer review to address reviewer comments, ensuring methodological rigor was maintained. Changes were only made with a minimum of 70% agreement and less than 15% disagreement among panel members. Deviations from the original protocol are documented in supplementary materials.
Invasive candidiasis
Background
Invasive candidiasis (IC) is the most common invasive fungal disease (IFD) among non-neutropenic, critically ill adults in the ICU, with mortality rates potentially exceeding 50% in septic shock cases. It occurs when Candida species invade sterile body areas. IC can manifest as candidemia or deep-seated candidiasis, with intra-abdominal candidiasis being the most prevalent deep-seated form in this population.
Development Process for Invasive Candidiasis Definitions
Candidemia is confirmed by isolating Candida from blood cultures obtained via venipuncture. In cases where a proven diagnosis is unavailable, patients with high probability of IC can be included in research. The expert panel evaluated clinical criteria, cultures from non-sterile sites, and fungal biomarkers, primarily focusing on serum (1,3)-β-D-glucan (BDG). However, the panel opted not to define a “probable” category for candidemia due to the high sensitivity of properly collected blood cultures.
For deep-seated candidiasis, a proven diagnosis is less common, and cultures from non-sterile sites along with biomarkers could help define probable cases in research. Despite discussions about using serum BDG, concerns about its specificity led the panel to exclude it as a criterion for defining probable deep-seated candidiasis.
Defining IC based solely on clinical suspicion poses challenges, leading the panel to reject the idea of a “possible” IC category to avoid including patients without IC, ensuring reliability and comparability in research findings.
Definitions of proven invasive candidiasis and probable deep-seated candidiasis
The developed definitions of proven IC and probable deep-seated candidiasis in non-neutropenic, critically ill adult ICU patients without classical host factors for IFD are detailed in Tables 1 and 2, respectively. A flowchart to identify patients fulfilling the definition of probable deep-seated candidiasis is also displayed in Fig. 1

Figure 1
Proven Invasive Candidiasis
The expert panel agreed that the identification of Candida species from sterile sites defines invasive candidiasis (IC), which can be either candidemia or deep-seated candidiasis. Diagnosis can be made via direct microscopy, culture, or histology. Histological evidence of budding Candida cells confirms proven IC, while polymerase chain reaction (PCR) or culture is needed for identifying hyphae or pseudohyphae, which can also appear in other yeasts.
Proven Invasive Candidiasis
To define probable deep-seated candidiasis, at least one mycological criterion and one clinical criterion must be met. The first mycological criterion is the recovery of Candida from a sterile specimen obtained from an abdominal, mediastinal, or pleural space after gastrointestinal or urogenital wall integrity has been compromised. Specimens should ideally be collected during surgery or from imaging-guided aspirates within 24 hours. The second mycological criterion involves the presence of proven candidemia as an indicator of probable deep-seated candidiasis in cases without perforation.
For clinical criteria, funduscopic lesions compatible with invasive candidiasis or unexplained radiological abnormalities in potential infection sites must be present. Detailed investigations to rule out alternative diagnoses should be documented in research studies employing this definition.
The panel noted that few studies adequately assessed PCR and fungal antigen-based biomarkers for diagnosing IC in non-neutropenic, critically ill adults. However, they recognize these tests as vital areas for future research to enhance IC diagnosis in both clinical and research contexts.
Invasive aspergillosis
Background
Invasive aspergillosis (IA) is typically seen in at-risk populations like hematology and solid organ transplant (SOT) patients, but it can also occur in non-neutropenic adults in the ICU. In these patients, IA often manifests as invasive pulmonary aspergillosis (IPA), which presents diagnostic challenges, including the absence of classic radiological signs and lower accuracy of non-culture tests like galactomannan. Histological diagnosis is often impractical due to patient conditions. Various definitions of probable IA have been proposed, but they lack broad consensus and are often limited to specific ICU populations.
Development Process for Invasive Aspergillosis Definitions
Developing a universal definition of IA in non-neutropenic ICU patients is complicated due to nonspecific symptoms and varied risk factors. A systematic review helped identify effective features from existing definitions and tests. Key findings included: the AspICU definition’s ability to distinguish colonization from infection in patients with positive respiratory cultures, and the superior diagnostic performance of bronchoalveolar lavage fluid (BALF) galactomannan over serum. The panel reached consensus on definitions for proven IA and probable IPA/tracheobronchial aspergillosis (TBA), but opted against a “possible” IA category for research due to the risk of false positives.
The definition of proven IA applies to all forms, but probable IA definitions are limited to IPA and TBA. The panel emphasized that specific predisposing conditions, rather than vague risk factors, should define probable IA to maintain research comparability. While this may seem conservative, it allows flexibility in clinical practice while ensuring robust research standards.
Definitions of proven invasive aspergillosis and probable invasive pulmonary aspergillosis/probable tracheobronchial aspergillosis
The definitions of proven IA and of probable IPA and probable TBA in non-neutropenic, critically ill adult ICU patients without classical host factors for IFD are detailed in Table 3 and Table 4, respectively. A flowchart to identify patients fulfilling the definition of probable IPA/probable TBA is also displayed in Fig. 2.

Table 3. Research definition for proven invasive aspergillosis in non-neutropenic, adult patients in ICU

Table 4. Research definitions for probable invasive pulmonary aspergillosis and tracheobronchial aspergillosis in non-neutropenic, adult patients in ICU

Figure 2
Proven Invasive Aspergillosis
Proven invasive aspergillosis (IA) in non-neutropenic, critically ill adult ICU patients is defined by the detection of Aspergillus species and tissue invasion. This includes histological or cytopathological evidence of tissue invasion from a normally sterile site or the lung, along with the detection of Aspergillus hyphae via culture or PCR. Additionally, recovery of Aspergillus from a biopsy or needle aspiration of a lesion consistent with an infectious process also qualifies as proven IA.
Probable Invasive Pulmonary Aspergillosis and Probable Tracheobronchial Aspergillosis
To classify as probable invasive pulmonary aspergillosis (IPA) or tracheobronchial aspergillosis (TBA), a patient must meet several criteria: at least one compatible sign or symptom, one ICU host factor, one clinical criterion, and one mycological criterion. Notably, for patients with COVID-19 or influenza, probable TBA can be defined even in the absence of compatible signs and symptoms.
Compatible Signs and Symptoms
Compatible signs and symptoms include persistent fever despite appropriate antibiotic therapy, relapse of fever after a period of defervescence, pleuritic chest pain, dyspnea, hemoptysis, and worsening respiratory insufficiency. These signs must align with the site and progression of IPA or TBA to proceed with the evaluation for research studies.
ICU Host Factors
ICU host factors include conditions such as influenza, COVID-19, moderate to severe chronic obstructive pulmonary disease (COPD), decompensated liver cirrhosis, uncontrolled HIV with a CD4 cell count less than 200/mm³, and solid tumors. These factors serve as important baseline information for defining probable IA.
Clinical Criteria
Clinical criteria for probable IPA/TBA include the presence of tracheobronchial ulceration, nodules, pseudomembranes, or plaques on bronchoscopy for TBA, and pulmonary infiltrates or cavitation not attributable to other causes on chest CT for IPA.
Mycological Criteria
The mycological criteria include the detection of mold elements in bronchoalveolar lavage fluid (BALF), positive Aspergillus culture from BALF, serum galactomannan levels greater than 0.5 optical density index (ODI), and BALF galactomannan levels of 1.0 ODI or higher. While PCR testing for Aspergillus may assist in diagnosis, its overall performance in non-neutropenic ICU patients is still being evaluated.
Future updates may incorporate PCR as a mycological criterion, particularly in research involving COVID-19 patients. Other tests, such as lateral flow assays, may also be considered for defining probable IPA/TBA, but galactomannan tests remain the preferred method when available, pending further evidence.
Other invasive fungal diseases
Definition development process
For IFD other than IC and IA, such as Pneumocystis jirovecii pneumonia (PJP), the systematic reviews supporting the development of this document highlighted the lack of sufficient evidence on the diagnostic performance of existing definitions and laboratory tests for their diagnosis in non-neutropenic, critically ill adult patients in the ICU [23]. While for proven IFD other than IA and IC, the expert panel suggested adhering to the definitions already provided in the EORTC/MSGERC consensus document [20], defining a probable category for these IFD was considered unfeasible in the population of interest. For this reason, dedicated initiatives have been started to assess the use and performance of diagnostic tests for IFD other than IC and IA in ICU patients [56, 57], aimed to support the development of definitions of probable disease in future updates of this document.
Conclusions
The FUNDICU consensus document provides definitions for IC and IA in non-neutropenic, adult patients in the ICU who do not fulfil the host factors included in the recent EORTC/MSGERC consensus document [20], for use in clinical research. Although many gaps remain, we hope that, if widely adopted, the standardized definitions provided in this document will facilitate the design of future research studies and increase the comparability of their results. The ultimate goal is to standardize the diagnosis of IFD and optimize the management and outcomes of critically ill patients with IFD.
Source: Bassetti, M., Giacobbe, D.R., Agvald-Ohman, C. et al. Invasive Fungal Diseases in Adult Patients in Intensive Care Unit (FUNDICU): 2024 consensus definitions from ESGCIP, EFISG, ESICM, ECMM, MSGERC, ISAC, and ISHAM. Intensive Care Med 50, 502–515 (2024).