Performance of Galactomannan Antigen, Beta-d-Glucan, and Aspergillus-Lateral-Flow Device for the Diagnosis of Invasive Aspergillosis

Implementation of Lateral Flow Assays for the Diagnosis of Invasive Aspergillosis in European Hospitals: A Survey from Belgium and a Literature Review of Test Performances in Different Patient Populations

OBJECTIVES

Diagnosis of invasive aspergillosis is based on a combination of criteria, of which the detection of Aspergillus galactomannan (GM) often is decisive. To date, the most commonly used method to determine GM is an enzyme-linked immune assay (EIA). But since a few years lateral flow assays (LFAs) were introduced, providing the possibility for rapid single sample testing. More and more LFAs are entering the market, but, although often being equated, all use their own antibodies, procedures and interpretation criteria. A recent European survey revealed that about 24-33% of laboratories implemented a lateral flow assay on-site.

METHODS

We conducted a survey at 81 Belgian hospital laboratories regarding the implementation of LFAs in their centre. In addition, we performed an extensive review of all publicly available studies on the performance of lateral flow assays to diagnose invasive aspergillosis.

RESULTS

Response rate to the survey was 69%. Of the 56 responding hospital laboratories, 6 (11%) used an LFA. The Soña Aspergillus galactomannan LFA (IMMY, Norman, Oklahoma, USA) was used in 4/6 centres, while two centres used the QuicGM (Dynamiker, Tianjin, China) and one centre used the FungiXpert Aspergillus Galactomannan Detection K-set LFA (Genobio [Era Biology Technology], Tianjin, China). One centre used 2 distinct LFAs. In 3/6 centres, the sample is sent to another lab for confirmation with GM-EIA when the LFA result is positive and in 2/6 when the LFA results is negative. In one centre, a confirmatory GM-EIA is always performed in house. In three centres the LFA result is used as a complete substitute for GM-EIA. Available LFA performance studies are very diverse and results vary in function of the study population and type of LFA. Apart from the IMMY and OLM LFA, only very limited performance data are available. From two out of three LFAs used in Belgium, no clinical performance studies are published in literature.

CONCLUSIONS

A large variety of LFAs are used in Belgian Hospitals, some of which no clinical validation studies are published. These results do likely have implications for other parts of Europe and for the rest of the world as well. Due to the variable performance of LFA tests and the limited validation data available, each laboratory must check the available performance information of the specific test considered for implementation. In addition, laboratories should perform an implementation verification study.

Evaluation of two lateral flow assays in BAL fluids for the detection of invasive pulmonary aspergillosis: A retrospective two-centre study

BACKGROUND

Commonly, the application of radiological and clinical criteria and the determination of galactomannan (GM) in respiratory samples are used as a diagnostic tool for the detection of invasive pulmonary aspergillosis (IPA).

MATERIALS/METHODS

In this study, two lateral flow assays, OLM Aspergillus lateral flow device (LFD) and IMMY sōna Aspergillus Galactomannan lateral flow assay (LFA), were evaluated at two tertiary hospitals in Germany. A total of 200 bronchoalveolar lavage (BAL) samples from patients with suspicion of IPA were analysed retrospectively. LFD and LFA were evaluated against four different criteria: Blot, EORTC/MSG, Schauwvlieghe and extended Blot criteria and additionally against GM.

RESULTS

The evaluation of four algorithms for the diagnosis of IPA showed that there exist good diagnostic tools to rule out an IPA even before results of Aspergillus culture are available. Sensitivities and negative predictive values are generally higher for the LFA than for the LFD in all four criteria. Specificity and positive predictive values varied depending on the classification criteria. The total agreement between the GM and the LFA cube reader (cut-off = 1) was 84%. The correlation between the GM and LFA was calculated with r = 0.8.

CONCLUSION

The here presented data indicate that a negative LFA result in BAL fluid can reliable rule out an IPA in a heterogeneous group of ICU patients based on the original Blot criteria. LFA seems to be a promising immunochromatographic test exhibiting a good agreement with positive GM values.

Performance of the (1,3)-Beta-D-Glucan Assay on Bronchoalveolar Lavage Fluid for the Diagnosis of Invasive Pulmonary Aspergillosis

Detection of (1,3)-beta-D-glucan (BDG), a component of the cell wall of many fungi, was studied in bronchoalveolar lavage fluid (BALF) as a possible aid for the diagnosis of proven/probable invasive pulmonary aspergillosis (IPA). BDG was measured on stored BALF from 13 patients with EORTC/MSGERC defined proven/probable IPA and 26 matched control patients without IPA. The median BALF BDG was 80 pg/mL (range < 45-8240 pg/mL) in the IPA cohort and 148 pg/mL (range < 45-5460 pg/mL) in the non-IPA cohort. Using a positive cutoff of ≥ 80 pg/mL, sensitivity was 54% and specificity was 38%. Higher cutoff values led to improvement in specificity but a dramatic decrease in sensitivity. ROC/AUC analysis was unable to identify an optimal cutoff value at which test performance was enhanced: AUC 0.43, 95% CI 0.24-0.63. When the BDG assay was performed on BALF, neither sensitivity nor specificity was sufficient for use in the diagnosis of IPA.

An Overview of the Management of the Most Important Invasive Fungal Infections in Patients with Blood Malignancies

In patients with hematologic malignancies due to immune system disorders, especially persistent febrile neutropenia, invasive fungal infections (IFI) occur with high mortality. Aspergillosis, candidiasis, fusariosis, mucormycosis, cryptococcosis and trichosporonosis are the most important infections reported in patients with hematologic malignancies that undergo hematopoietic stem cell transplantation. These infections are caused by opportunistic fungal pathogens that do not cause severe issues in healthy individuals, but in patients with hematologic malignancies lead to disseminated infection with different clinical manifestations. Prophylaxis and creating a safe environment with proper filters and air pressure for patients to avoid contact with the pathogens in the surrounding environment can prevent IFI. Furthermore, due to the absence of specific symptoms in IFI, rapid and accurate diagnosis reduces the mortality rate of these infections and using molecular techniques along with standard mycological methods will improve the diagnosis of disseminated fungal infection in patients with hematologic disorders. Amphotericin B products, extended-spectrum azoles, and echinocandins are the essential drugs to control invasive fungal infections in patients with hematologic malignancies, and according to various conditions of patients, different results of treatment with these drugs have been reported in different studies. On the other hand, drug resistance in recent years has led to therapeutic failures and deaths in patients with blood malignancies, which indicates the need for antifungal susceptibility tests to use appropriate therapies. Life-threatening fungal infections have become more prevalent in patients with hematologic malignancies in recent years due to the emergence of new risk factors, new species, and increased drug resistance. Therefore, in this review, we discuss the different dimensions of the most critical invasive fungal infections in patients with hematologic malignancies and present a list of these infections with different clinical manifestations, treatment, and outcomes.

Identification of Mycoses in Developing Countries

Extensive advances in technology offer a vast variety of diagnostic methods that save time and costs, but identification of fungal species causing human infections remains challenging in developing countries. Since the echinocandins, antifungals widely used to treat invasive mycoses, are still unavailable in developing countries where a considerable number of problematic fungal species are present, rapid and reliable identification is of paramount importance. Unaffordability, large footprints, lack of skilled personnel, and high costs associated with maintenance and infrastructure are the main factors precluding the establishment of high-precision technologies that can replace inexpensive yet time-consuming and inaccurate phenotypic methods. In addition, point-of-care lateral flow assay tests are available for the diagnosis of Aspergillus and Cryptococcus and are highly relevant for developing countries. An Aspergillus galactomannan lateral flow assay is also now available. Real-time PCR remains difficult to standardize and is not widespread in countries with limited resources. Isothermal and conventional PCR-based amplification assays may be alternative solutions. The combination of real-time PCR and serological assays can significantly increase diagnostic efficiency. However, this approach is too expensive for medical institutions in developing countries. Further advances in next-generation sequencing and other innovative technologies such as clustered regularly interspaced short palindromic repeats (CRISPR)-based diagnostic tools may lead to efficient, alternate methods that can be used in point-of-care assays, which may supplement or replace some of the current technologies and improve the diagnostics of fungal infections in developing countries.

Evaluation of a Novel Aspergillus Antigen Enzyme-Linked Immunosorbent Assay

Invasive aspergillosis (IA) is a life-threatening infection that mainly occurs in immunocompromised patients. Here, we compared the novel Aspergillus-specific galactomannoprotein (GP) enzyme-linked immunosorbent assay (ELISA) (Euroimmun Medizinische Labordiagnostika AG) to the established Platelia Aspergillus galactomannan (GM) ELISA (Bio-Rad Laboratories) for the detection of IA.

Invasive aspergillosis (IA) is a life-threatening infection that mainly occurs in immunocompromised patients. Here, we compared the novel Aspergillus-specific galactomannoprotein (GP) enzyme-linked immunosorbent assay (ELISA) (Euroimmun Medizinische Labordiagnostika AG) to the established Platelia Aspergillus galactomannan (GM) ELISA (Bio-Rad Laboratories) for the detection of IA. A total of 267 serum samples from 45 cases of proven and 4 episodes of probable IA (according to European Organization for Research and Treatment of Cancer/Invasive Fungal Infections Cooperative Group and the National Institute of Allergy and Infectious Diseases Mycoses Study Group [EORTC/MSG] criteria) and 156 sera from patients without evidence of IA were tested. Pearson’s correlation statistics, as well as sensitivity and specificity, were calculated using manufacturer-recommended (GM) or optimized (GP) cutoff levels. Aspergillus fumigatus was found in 88% of culture-positive infections. When we analyzed all 423 serum samples, GM and GP tests correlated strongly (r = 0.82, P < 0.0001). Among proven IA cases using samples obtained as closely as possible to the day of proven diagnosis, the sensitivity for both tests was 40%. All cases of probable IA (defined by positive GM testing) were also GP positive. Concordant results of the two ELISAs were obtained in 43 of 49 samples (88%). Extending measurements to all sera available in the time frame of 7 days prior to 7 days after the day of proven diagnosis, 47% and 56% of the cases were detected by the GM and GP tests, respectively. Specificity was 99% for GM and 96% for GP testing. For the diagnosis of IA, sensitivity and specificity of the novel GP ELISA are similar to those of the Platelia GM ELISA. The low sensitivities of both tests underline the need for serial testing in patients at risk for IA.

Use of 1,3-β-D-glucan in invasive fungal diseases in hematology patients

INTRODUCTION

Invasive fungal diseases (IFD) remain a leading cause of morbidity and mortality in hematology patients. Within a diagnostic-driven approach, the use of the serum (1,3)-ß-D-glucan (BDG) test represents a valid tool for the early diagnosis and treatment of IFD. Areas covered: The available literature on the use of BDG in hematology patients was systematically retrieved. Then, it was reviewed and discussed, to identify key issues pertaining to a clinically-oriented narrative presentation of the topic. Expert commentary: The use of BDG in hematology patients at risk for invasive aspergillosis (IA) is secondary to the use of galactomannan. However, since BDG is not specific for IA, it offers an advantage of diagnosing also other IFD, such as candidiasis and pneumocystosis. The limitations of BDG include high costs and lower sensitivity in hematology patients compared to other cohorts. The risk of false positive results is possibly lower in real life than in theory, since glucan-free equipment is available and modern dialysis membranes and blood products usually do not release BDG. Thus, in experienced hands and selected clinical situations, BDG is a useful diagnostic tool, particularly due to short turnover time to results and versatility in diagnosing different IFD.

Lateral Flow Assays for the Diagnosis of Invasive Aspergillosis: Current Status

PURPOSE OF REVIEW

Diagnosis during early stages of invasive aspergillosis (IA) and targeted antifungal treatment has the potential to improve survival significantly. Despite advances in the diagnostic arsenal, invasive mold infections remain difficult to diagnose-especially at early stages before typical radiological signs develop. Varying availability and time-to-results are important limitations of current approved biomarkers and molecular assays for diagnosis of IA. Here, we will give an update on the Aspergillus-specific lateral-flow device (LFD) test. We further review promising findings on feasibility of point-of-care (POC) detection of urinary excreted fungal galactomannan-like antigens.

RECENT FINDINGS

POC LFD assays for detection of Aspergillus antigens are currently in development. The Aspergillus-specific LFD test, which is based on the JF5 antibody (Ab), detects an extracellular glycoprotein antigen secreted during active growth of Aspergillus spp. The test has shown promising results in various studies. In addition, a monoclonal Ab476-based LFD for POC detection of urinary excreted fungal galactomannan-like antigens has been developed but needs further validation.

SUMMARY

Important advances have been made in the development of LFD assays for IA. Most promising is the Aspergillus-specific LFD test; commercial availability is still pending, however. The search for reliable POC tests for other molds, including mucorales, continues.