Molecular and Nonmolecular Diagnostic Methods for Invasive Fungal Infections

Abstract

SUMMARY Invasive fungal infections constitute a serious threat to an ever-growing population of immunocompromised individuals and other individuals at risk. Traditional diagnostic methods, such as histopathology and culture, which are still considered the gold standards, have low sensitivity, which underscores the need for the development of new means of detecting fungal infectious agents. Indeed, novel serologic and molecular techniques have been developed and are currently under clinical evaluation. Tests like the galactomannan antigen test for aspergillosis and the β-glucan test for invasive Candida spp. and molds, as well as other antigen and antibody tests, for Cryptococcus spp., Pneumocystis spp., and dimorphic fungi, have already been established as important diagnostic approaches and are implemented in routine clinical practice. On the other hand, PCR and other molecular approaches, such as matrix-assisted laser desorption ionization (MALDI) and fluorescence in situ hybridization (FISH), have proved promising in clinical trials but still need to undergo standardization before their clinical use can become widespread. The purpose of this review is to highlight the different diagnostic approaches that are currently utilized or under development for invasive fungal infections and to identify their performance characteristics and the challenges associated with their use.

Advances Against Aspergillosis: Biology, Host response, Diagnosis and Treatment

“…Reliable early diagnosis of aspergillosis continues to be a challenge for the clinician because of nonspecific signs of infection, as well as limitations in the sensitivity or specificity of current diagnostic methods [23]. Guinea and Bouza [24] address these current issues and present evidence to support improved diagnosis with newer technologies, such as lateral flow techniques, and DNA technology.…”

Antifungal stewardship considerations for adults and pediatrics

“…A discussion of each test and its specifications is beyond the scope of this paper but has already been extensively reviewed. 19,48 In a recent study, Nguyen et al compared the performance of a validated Candida real-time PCR and BDG to blood culture in 55 patients with IC and found that both tests were more sensitive than blood cultures among patients with deep-seated infection, signifying their usefulness as diagnostic adjuncts (88% and 62% vs 17%; P D 0.0005 and P D 0.003). 54 Another promising assay is the T2Candida Panel (T2 Biosystems), a US Food and Drug Administration (FDA)-cleared test to detect 5 species of Candida directly from whole blood without need for culture or nucleic acid extraction within 3 to 5 hours (Table 1).…”

“…These include matrix-assisted laser desorption/ ionization time-of-flight (MALDI-TOF) spectrometry, multiplex PCR, and peptide nucleic acid fluorescent in situ hybridization (PNA FISH). 19,49 Test characteristics for all 3 are described in Table 1.…”

“…[14][15][16][17][18] The difficulty in establishing an early diagnosis is related to the nonspecific clinical features and the low sensitivity of microscopy, histologic examination, conventional radiology, and cultures. 19 Recognizing the difficulties in diagnosis plus the awareness of harm associated with delays in appropriate treatment has prompted many clinicians to choose to empirically start antifungal treatment. There is also keen interest in prophylactic strategies to prevent IFI in highrisk patients.…”

“…Attention has thus turned to the application of non-culturebased methods, and previous reviews have detailed the test performance and caveats of using BDG, galactomannan (GM) antigen detection, and PCR. 19,60 In general, results of non-culture-based tests should be interpreted in conjunction with other clinical, radiographic, and microbiologic criteria for IA. 61,62 With respect to serum BDG and GM assays, several meta-analyses have noted heterogeneity of results attributed to differences in study design, patient populations (e.g., hematologic vs other), the criteria used to define a positive test, and the definition of IA.…”