This study evaluates the diagnostic value of non-conventional microbiological methods for early detection of candidemia and invasive candidiasis in adult hospitalized patients with suspected invasive fungal infection. Conventional blood culture remains the gold standard for diagnosis but has limited sensitivity and may delay initiation of targeted antifungal therapy.

The study investigates whether the combined use of serum biomarkers (1,3)-β-D-glucan, mannan and anti-mannan antibodies, and molecular detection of Candida DNA by PCR improves the diagnostic performance compared with conventional culture-based methods.

In addition, the study explores the host cytokine response associated with different Candida species and other fungal pathogens. The goal is to support the development of an optimized diagnostic algorithm for invasive fungal disease and improve clinical management of critically ill patients.

Early diagnosis of invasive fungal infections, particularly candidemia and invasive candidiasis, is essential for timely initiation of appropriate antifungal therapy and improvement of patient outcomes. Despite being considered the current diagnostic gold standard, blood culture has limited sensitivity and may remain negative in a substantial proportion of patients with invasive candidiasis. In addition, culture-based identification of fungal pathogens is time-consuming and may delay targeted treatment decisions.

To address these limitations, alternative diagnostic approaches have been developed, including detection of fungal cell wall biomarkers and molecular assays. Serum biomarkers such as (1,3)-β-D-glucan, mannan antigen, and anti-mannan antibodies may provide earlier indication of invasive Candida infection compared with blood culture. Molecular detection of Candida DNA by polymerase chain reaction (PCR) may also offer higher sensitivity and faster turnaround time.

This interventional diagnostic study evaluates the clinical and diagnostic utility of a combined non-conventional microbiological testing panel in adult patients with clinical suspicion of invasive/systemic fungal infection and risk factors for invasive fungal disease (e.g., ICU admission, central venous catheters, broad-spectrum antibiotics, parenteral nutrition, corticosteroid therapy, chemotherapy, immunosuppression, neutropenia, hemodialysis, mechanical ventilation, and Candida colonization).

Participants undergo routine blood culture testing for bacteria and fungi as part of standard clinical care. In addition, blood samples are collected for the following diagnostic tests:

Serum (1,3)-β-D-glucan

Mannan antigen and anti-mannan antibodies

PCR-based detection of Candida DNA from EDTA whole blood

Samples are processed according to routine laboratory procedures in participating microbiology laboratories. Blood culture-positive Candida isolates are identified and stored for further analyses. Participants are categorized into study groups based on blood culture results (Candida-positive blood culture group, bacterial-positive blood culture group, and blood culture-negative group). A healthy volunteer control group may be included for comparative purposes.

The primary objective is to determine whether the combined non-conventional diagnostic panel improves detection of candidemia/invasive candidiasis compared with conventional blood culture alone. Secondary objectives include evaluation of the diagnostic performance of individual biomarkers and PCR testing, assessment of the time to diagnosis, and analysis of host cytokine response patterns associated with different fungal pathogens.

The overall aim of the study is to support the development of an optimized diagnostic algorithm for invasive fungal disease, improve early detection, and reduce unnecessary or delayed antifungal treatment in critically ill patients.

Inclusion Criteria:

• Adult hospitalized patients (≥18 years)
• Clinical suspicion of invasive/systemic fungal infection (suspected fungal sepsis)
• Presence of risk factors for invasive fungal disease (e.g., ICU admission, central/peripheral venous catheters, parenteral nutrition, broad-spectrum antibiotic therapy >3 days, corticosteroid therapy, chemotherapy, immunosuppression, neutropenia, hemodialysis, mechanical ventilation, or Candida colonization)

Exclusion Criteria:

• Age <18 years
• Insufficient blood sample for additional diagnostic testing
• Refusal or inability to provide informed consent (if applicable)