Laboratory innovations to diagnose invasive mould infections—what is relevant, what is not?

Abstract

Background

Invasive mould infections (IMI) carry high morbidity and mortality. Conventional diagnostics—histopathology, culture and microscopy—rely on invasive sampling and lack sensitivity, particularly during early phases of infection. Rare and mixed mould infections are frequently diagnosed too late or missed.

Objectives

To provide a narrative review of recent innovations in diagnosing IMIs, highlighting advances, identifying areas where progress remains limited, and assessing gaps in current diagnostic algorithms to guide future directions.

Sources

We performed a literature search regarding diagnostic methods for IMIs without date restrictions, including experimental and clinical studies, systematic reviews and meta-analyses.

Content

Rapid lateral flow assays and single-sample chemiluminescent immunoassays for detecting Aspergillus antigens in blood and bronchoalveolar lavage fluid now complement enzyme immunoassays. Novel targets, such as urinary glycans and siderophores in various biological matrices, show potential to diagnose IMI. Targeted PCRs for Aspergillus and Mucorales enable earlier detection than conventional methods and rapid detection of resistance in case of A. fumigatus, although isolated Aspergillus PCR positivity is challenging to interpret. Metagenomic next-generation sequencing expands pathogen detection but is limited by costs and technical and interpretative challenges. A shift towards assays based on the host immune response (functional immune assays and biochemical markers) shows promise but remains investigational.

Implications

Due to different commercially available test formats, Aspergillus antigen detection assays can now be implemented in many hospitals. Implementation of Mucorales PCR tests improves the diagnosis of mucormycosis also in the setting of coinfections. Multimodal pathogen-based strategies that integrate antigen assays, targeted PCRs, and, in select cases, metagenomic next-generation sequencing enable earlier, more accurate, and comprehensive diagnosis of IMIs, ultimately improving clinical outcomes; but the need for rapid, accurate, noninvasive diagnostic tests for IMIs remains. Host-response–based assays are not yet clinic-ready. Prospective multicentre studies are needed to standardize diagnostic thresholds, validate novel diagnostic markers and to evaluate impact on patient outcomes and cost-effectiveness.