Recent progress in the diagnosis of fungal infections in the immunocompromised host

The management of invasive fungal infections has been hampered by the inability to diagnose the infection at an early stage of disease. Although proving the presence of infection by histology and culture remains the cornerstone of the diagnosis, non-culture based methods are becoming available that enable early detection. Molecular diagnosis by PCR appears very promising since fungal DNA can be detected in the blood of infected patients before conventional methods. Furthermore, a broad range of yeasts and molds can be identified to species level. Automation of sample preparation and use of real-time PCR systems will help standardize the procedure and reduce false positive results due to contamination. Promising assays for the detection of fungal antigens in serum have been commercialized, including detection systems for mannan (Candida) and galactomannan (Aspergillus). Circulating antigens can be detected at an early stage of infection, often before the onset of clinical symptoms. Antigen detection is limited to detecting only one genus and not enabling speciation. Furthermore, both PCR and antigen detection can be used to monitor the response of patients to treatment with anti-fungal agents. Although prospective screening of high-risk patients for the presence of circulating markers of fungal infection appears to be an appropriate strategy, studies are needed to help to establish the optimal approach to managing invasive fungal infections that incorporates the benefits of non-culture based methods.