Galactomannan antigenemia detection for diagnosis of invasive aspergillosis, part I

Improved Detection of Invasive Pulmonary Aspergillosis Arising during Leukemia Treatment Using a Panel of Host Response Proteins and Fungal Antigens

Invasive pulmonary aspergillosis (IPA) is an opportunistic fungal infection in patients undergoing chemotherapy for hematological malignancy, hematopoietic stem cell transplant, or other forms of immunosuppression. In this group, Aspergillus infections account for the majority of deaths due to mold pathogens. Although early detection is associated with improved outcomes, current diagnostic regimens lack sensitivity and specificity. Patients undergoing chemotherapy, stem cell transplantation and lung transplantation were enrolled in a multi-site prospective observational trial. Proven and probable IPA cases and matched controls were subjected to discovery proteomics analyses using a biofluid analysis platform, fractionating plasma into reproducible protein and peptide pools. From 556 spots identified by 2D gel electrophoresis, 66 differentially expressed post-translationally modified plasma proteins were identified in the leukemic subgroup only. This protein group was rich in complement components, acute-phase reactants and coagulation factors. Low molecular weight peptides corresponding to abundant plasma proteins were identified. A candidate marker panel of host response (9 plasma proteins, 4 peptides), fungal polysaccharides (galactomannan), and cell wall components (β-D glucan) were selected by statistical filtering for patients with leukemia as a primary underlying diagnosis. Quantitative measurements were developed to qualify the differential expression of the candidate host response proteins using selective reaction monitoring mass spectrometry assays, and then applied to a separate cohort of 57 patients with leukemia. In this verification cohort, a machine learning ensemble-based algorithm, generalized pathseeker (GPS) produced a greater case classification accuracy than galactomannan (GM) or host proteins alone. In conclusion, Integration of host response proteins with GM improves the diagnostic detection of probable IPA in patients undergoing treatment for hematologic malignancy. Upon further validation, early detection of probable IPA in leukemia treatment will provide opportunities for earlier interventions and interventional clinical trials.

Diagnosis of invasive aspergillosis by galactomannan antigenemia detection using an enzyme immunoassay

Invasive aspergillosis is a serious and often fatal infection in patients who are neutropenic or have undergone solid organ or stem cell transplantation. Delayed diagnosis and therapy may lead to poor outcomes. Diagnosis may be facilitated by a test for galactomannan antigen detection using an enzyme immunoassay. Other rapid methods for diagnosis include (1-->3)-beta-D: -glucan determination and polymerase chain reaction. The sensitivity and specificity of galactomannan antigenemia testing in serum and bronchoalveolar lavage specimens are high in patients with hematological malignancy, neutropenia, and receipt of stem-cell transplants. False positivity can be seen with concomitant administration of some antibiotics and infection by fungi other than Aspergillus.

Cross-reactivity of non-Aspergillus fungal species in the Aspergillus galactomannan enzyme immunoassay

The Aspergillus galactomannan enzyme-linked immunosorbant assay (EIA) has been demonstrated to facilitate rapid and sensitive detection of invasive aspergillosis. However, test specificity has not been fully evaluated in non-Aspergillus fungal species. Of 53 fungal isolates, cross-reactivity was observed with 5 non-Aspergillus spp.: Blastomyces dermatitidis, Nigrospora oryzae, Paecilomyces lilacinus, Penicillium chrysogenum, and Trichothecium roseum.

Antigen detection, serology, and molecular diagnosis of invasive mycoses in the immunocompromised host

Understanding the uses and limitations of methods for rapid diagnosis of fungal disease is essential in order to diagnose and treat these infections early in their course. Antigen detection methods are useful for diagnosis of aspergillosis, cryptococcosis, histoplasmosis, blastomycosis, paracoccidioidomycosis, and penicilliosis marneffei. The accuracy of the beta-glucan assay for diagnosis of aspergillosis and candidiasis and its role in fungal diagnosis remains unclear, in part because the few published studies report widely varying specificity. Serologic tests for antibodies are also useful for diagnosis of histoplasmosis and coccidioidomycosis, but their sensitivity may be reduced by immunosuppression. While molecular diagnostic methods have been described and are available at some reference and university laboratories, their role in patient care remains uncertain, largely because of the lack of well-characterized assays and studies establishing their accuracy. Culture methods, although essential for establishing the diagnosis in some cases, have limitations for rapid diagnosis, namely insensitivity, need for invasive procedures, and delayed growth.