Polymerase chain reaction for diagnosing invasive aspergillosis: getting closer but still a ways to go

Superior Accuracy of Aspergillus Plasma Cell-Free DNA Polymerase Chain Reaction Over Serum Galactomannan for the Diagnosis of Invasive Aspergillosis

BACKGROUND

Invasive aspergillosis (IA) in immunocompromised hosts carries high morbidity and mortality. Diagnosis is often delayed because definitive diagnosis requires invasive specimen collection, while noninvasive testing with galactomannan is moderately accurate. Plasma cell-free DNA polymerase chain reaction (cfDNA PCR) represents a novel testing modality for the noninvasive diagnosis of invasive fungal disease (IFD). We directly compared the performance of Aspergillus plasma cfDNA PCR with serum galactomannan for the diagnosis of IA during routine clinical practice.

METHODS

We conducted a retrospective study of all patients with suspected IFD who had Aspergillus plasma cfDNA PCR testing at Stanford Health Care from 1 September 2020 to 30 October 2022. Patients were categorized into proven, probable, possible, and no IA based on the EORTC/MSG definitions. Primary outcomes included the clinical sensitivity and specificity for Aspergillus plasma cfDNA PCR and galactomannan.

RESULTS

Overall, 238 unique patients with Aspergillus plasma cfDNA PCR test results, including 63 positives and 175 nonconsecutive negatives, were included in this study. The majority were immunosuppressed (89.9%) with 22.3% 30-day all-cause mortality. The overall sensitivity and specificity of Aspergillus plasma cfDNA PCR were 86.0% (37 of 43; 95% confidence interval [CI], 72.7-95.7) and 93.1% (121 of 130; 95% CI, 87.4-96.3), respectively. The sensitivity and specificity of serum galactomannan in hematologic malignancies/stem cell transplants were 67.9% (19 of 28; 95% CI, 49.3-82.1) and 89.8% (53 of 59; 95% CI, 79.5-95.3), respectively. The sensitivity of cfDNA PCR was 93.0% (40 of 43; 95% CI, 80.9-98.5) in patients with a new diagnosis of IA.

CONCLUSIONS

Aspergillus plasma cfDNA PCR represents a more sensitive alternative to serum galactomannan for noninvasive diagnosis of IA.

An Overview of Systematic Reviews of Polymerase Chain Reaction (PCR) for the Diagnosis of Invasive Aspergillosis in Immunocompromised People: A Report of the Fungal PCR Initiative (FPCRI)-An ISHAM Working Group

This overview of reviews (i.e., an umbrella review) is designed to reappraise the validity of systematic reviews (SRs) and meta-analyses related to the performance of Aspergillus PCR tests for the diagnosis of invasive aspergillosis in immunocompromised patients. The methodological quality of the SRs was assessed using the AMSTAR-2 checklist; the quality of the evidence (QOE) within each SR was appraised following the GRADE approach. Eight out of 12 SRs were evaluated for qualitative and quantitative assessment. Five SRs evaluated Aspergillus PCR on bronchoalveolar lavage fluid (BAL) and three on blood specimens. The eight SRs included 167 overlapping reports (59 evaluating PCR in blood specimens, and 108 in BAL), based on 107 individual primary studies (98 trials with a cohort design, and 19 with a case-control design). In BAL specimens, the mean sensitivity and specificity ranged from 0.57 to 0.91, and from 0.92 to 0.97, respectively (QOE: very low to low). In blood specimens (whole blood or serum), the mean sensitivity ranged from 0.57 to 0.84, and the mean specificity from 0.58 to 0.95 (QOE: low to moderate). Across studies, only a low proportion of AMSTAR-2 critical domains were unmet (1.8%), demonstrating a high quality of methodological assessment. Conclusions. Based on the overall methodological assessment of the reviews included, on average we can have high confidence in the quality of results generated by the SRs.

Rapid Detection of Azole-Resistant Aspergillus fumigatus in Clinical and Environmental Isolates by Use of a Lab-on-a-Chip Diagnostic System

Aspergillus fumigatus has widely evolved resistance to the most commonly used class of antifungal chemicals, the azoles. Current methods for identifying azole resistance are time-consuming and depend on specialized laboratories. There is an urgent need for rapid detection of these emerging pathogens at point-of-care to provide the appropriate treatment in the clinic and to improve management of environmental reservoirs to mitigate the spread of antifungal resistance. Our study demonstrates the rapid and portable detection of the two most relevant genetic markers linked to azole resistance, the mutations TR34 and TR46, found in the promoter region of the gene encoding the azole target cyp51A. We developed a lab-on-a-chip platform consisting of: (i) tandem-repeat loop-mediated isothermal amplification; (ii) state-of-the-art complementary metal-oxide-semiconductor microchip technology for nucleic acid amplification detection; and (iii) a smartphone application for data acquisition, visualization, and cloud connectivity. Specific and sensitive detection was validated with isolates from clinical and environmental samples from 6 countries across 5 continents, showing a lower limit of detection of 10 genomic copies per reaction in less than 30 min. When fully integrated with a sample preparation module, this diagnostic system will enable the detection of this ubiquitous fungus at the point-of-care, and could help to improve clinical decision making, infection control, and epidemiological surveillance.

Polymerase chain reaction blood tests for the diagnosis of invasive aspergillosis in immunocompromised people

BACKGROUND

This is an update of the original review published in the Cochrane Database of Systematic Reviews Issue 10, 2015.Invasive aspergillosis (IA) is the most common life-threatening opportunistic invasive mould infection in immunocompromised people. Early diagnosis of IA and prompt administration of appropriate antifungal treatment are critical to the survival of people with IA. Antifungal drugs can be given as prophylaxis or empirical therapy, instigated on the basis of a diagnostic strategy (the pre-emptive approach) or for treating established disease. Consequently, there is an urgent need for research into both new diagnostic tools and drug treatment strategies. Increasingly, newer methods such as polymerase chain reaction (PCR) to detect fungal nucleic acids are being investigated.

OBJECTIVES

To provide an overall summary of the diagnostic accuracy of PCR-based tests on blood specimens for the diagnosis of IA in immunocompromised people.

SEARCH METHODS

We searched MEDLINE (1946 to June 2015) and Embase (1980 to June 2015). We also searched LILACS, DARE, Health Technology Assessment, Web of Science and Scopus to June 2015. We checked the reference lists of all the studies identified by the above methods and contacted relevant authors and researchers in the field. For this review update we updated electronic searches of the Cochrane Central Register of Controlled Trials (CENTRAL; 2018, Issue 3) in the Cochrane Library; MEDLINE via Ovid (June 2015 to March week 2 2018); and Embase via Ovid (June 2015 to 2018 week 12).

SELECTION CRITERIA

We included studies that: i) compared the results of blood PCR tests with the reference standard published by the European Organisation for Research and Treatment of Cancer/Mycoses Study Group (EORTC/MSG); ii) reported data on false-positive, true-positive, false-negative and true-negative results of the diagnostic tests under investigation separately; and iii) evaluated the test(s) prospectively in cohorts of people from a relevant clinical population, defined as a group of individuals at high risk for invasive aspergillosis. Case-control and retrospective studies were excluded from the analysis.

DATA COLLECTION AND ANALYSIS

Authors independently assessed quality and extracted data. For PCR assays, we evaluated the requirement for either one or two consecutive samples to be positive for diagnostic accuracy. We investigated heterogeneity by subgroup analyses. We plotted estimates of sensitivity and specificity from each study in receiver operating characteristics (ROC) space and constructed forest plots for visual examination of variation in test accuracy. We performed meta-analyses using the bivariate model to produce summary estimates of sensitivity and specificity.

MAIN RESULTS

We included 29 primary studies (18 from the original review and 11 from this update), corresponding to 34 data sets, published between 2000 and 2018 in the meta-analyses, with a mean prevalence of proven or probable IA of 16.3 (median prevalence 11.1% , range 2.5% to 57.1%). Most patients had received chemotherapy for haematological malignancy or had undergone hematopoietic stem cell transplantation. Several PCR techniques were used among the included studies. The sensitivity and specificity of PCR for the diagnosis of IA varied according to the interpretative criteria used to define a test as positive. The summary estimates of sensitivity and specificity were 79.2% (95% confidence interval (CI) 71.0 to 85.5) and 79.6% (95% CI 69.9 to 86.6) for a single positive test result, and 59.6% (95% CI 40.7 to 76.0) and 95.1% (95% CI 87.0 to 98.2) for two consecutive positive test results.

AUTHORS' CONCLUSIONS

PCR shows moderate diagnostic accuracy when used as screening tests for IA in high-risk patient groups. Importantly the sensitivity of the test confers a high negative predictive value (NPV) such that a negative test allows the diagnosis to be excluded. Consecutive positives show good specificity in diagnosis of IA and could be used to trigger radiological and other investigations or for pre-emptive therapy in the absence of specific radiological signs when the clinical suspicion of infection is high. When a single PCR positive test is used as the diagnostic criterion for IA in a population of 100 people with a disease prevalence of 16.3% (overall mean prevalence), three people with IA would be missed (sensitivity 79.2%, 20.8% false negatives), and 17 people would be unnecessarily treated or referred for further tests (specificity of 79.6%, 21.4% false positives). If we use the two positive test requirement in a population with the same disease prevalence, it would mean that nine IA people would be missed (sensitivity 59.6%, 40.4% false negatives) and four people would be unnecessarily treated or referred for further tests (specificity of 95.1%, 4.9% false positives). Like galactomannan, PCR has good NPV for excluding disease, but the low prevalence of disease limits the ability to rule in a diagnosis. As these biomarkers detect different markers of disease, combining them is likely to prove more useful.

Rapid and Sensitive Detection of Azole-Resistant Aspergillus fumigatus by Tandem Repeat Loop-Mediated Isothermal Amplification

Invasive fungal infections caused by multiazole-resistant Aspergillus fumigatus are associated with increasing rates of mortality in susceptible patients. Current methods of diagnosing infections caused by multiazole-resistant A. fumigatus are, however, not well suited for use in clinical point-of-care testing or in the field. Loop-mediated isothermal amplification (LAMP) is a widely used method of nucleic acid amplification with rapid and easy-to-use features, making it suitable for use in different resource settings. Here, we developed a LAMP assay to detect a 34 bp tandem repeat, named TR34-LAMP. TR34 is a high-prevalence allele that, in conjunction with the L98H single-nucleotide polymorphism, is associated with the occurrence of multiazole resistance in A. fumigatus in the environment and in patients. This process was validated with both synthetic double-stranded DNA and genomic DNA prepared from azole-resistant isolates of A. fumigatus. Use of our assay resulted in rapid and specific identification of the TR34 allele with high sensitivity, detecting down to 10 genomic copies per reaction within 25 minutes. Fluorescent and colorimetric detections were used for the analysis of 11 clinical isolates as cross validation. These results show that the TR34-LAMP assay has the potential to accelerate the screening of clinical and environmental A. fumigatus to provide a rapid and accurate diagnosis of azole resistance, which current methods struggle to achieve.

Diagnosis of invasive fungal diseases in haematology and oncology: 2018 update of the recommendations of the infectious diseases working party of the German society for hematology and medical oncology (AGIHO)

Invasive fungal diseases (IFD) are a primary cause of morbidity and mortality in patients with haematological malignancies. These infections are mostly life-threatening and an early diagnosis and initiation of appropriate antifungal therapy are essential for the clinical outcome. Most commonly, Aspergillus and Candida species are involved. However, other Non-Aspergillus moulds are increasingly identified in case of documented IFD. For definite diagnosis of IFD, a combination of diagnostic tools have to be applied, including conventional mycological culture and non-conventional microbiological tests such as antibody/antigen and molecular tests, as well as histopathology and radiology. Although varying widely in cancer patients, the risk of invasive fungal infection is highest in those with allogeneic stem cell transplantation and those with acute leukaemia and markedly lower in patients with solid cancer. Since the last edition of Diagnosis of Invasive Fungal Diseases recommendations of the German Society for Hematology and Oncology in 2012, integrated care pathways have been proposed for the management and therapy of IFDs with either a diagnostic driven strategy as opposed to a clinical or empirical driven strategy. This update discusses the impact of this additional evidence and effective revisions.

Special considerations for the diagnosis and treatment of invasive pulmonary aspergillosis

INTRODUCTION

The diagnosis and treatment of invasive pulmonary aspergillosis (IPA) are ongoing challenges in clinical practice. While important advances have recently been made, including enhanced diagnostic modalities as well as novel therapeutic and prophylactic options, more effective options are urgently needed as the population of immunocompromised patients continues to expand. Areas covered: In this paper, we review novel approaches to diagnosis of IPA, including multiplex PCR, Matrix Assisted Laser Desorption/Ionization-Time of Flight Mass Spectrometry and provide a detailed review of the extended-spectrum triazole isavuconazole, which was approved in 2015 to treat IPA. Expert commentary: We explore burgeoning approaches to diagnosis, including the lateral flow assay, volatile organic compounds, and artificial olfactory technology, as well as novel antifungal agents to treat IPA such as SCY-078 and F901318.

Isolation of Nucleic Acids for Fungal Diagnosis

PCR can aid in the diagnosis of invasive fungal disease (IFD). While the large number of "in-house" methodologies drives technological diversity, providing robustness, they make it difficult to identify optimal strategies, limiting standardization, and widespread acceptance. No matter how efficient, PCR utility will be limited by the quality of extracted nucleic acid. This chapter highlights benefits and limitations affecting the nucleic acid extraction process, before focusing on recent recommendations that through multicenter evaluation have provided optimal and standardized methodology.

Recent developments in the management of invasive fungal infections in patients with oncohematological diseases

Patients with hematological cancer have a high risk of invasive fungal diseases (IFDs). These infections are mostly life threatening and an early diagnosis and initiation of appropriate antifungal therapy are essential for the clinical outcome. Most commonly, Aspergillus and Candida species are involved. However, other non-Aspergillus molds are increasingly be identified in cases of documented IFDs. Important risk factors are long lasting granulocytopenia with neutrophil counts below 500/μl for more than 10 days or graft-versus-host disease resulting from allogeneic stem-cell transplantation. For definite diagnosis of IFD, various diagnostic tools have to be applied, including conventional mycological culture and nonconventional microbiological tests such as antibody/antigen and molecular tests, as well as histopathology and radiology. In the last few years, various laboratory methods, like the Aspergillus GM immunoassay (Aspergillus GM EIA), 1,3-ß-D-glucan (BG) assay or polymerase chain reaction (PCR) techniques have been developed for better diagnosis. Since no single indirect test, including radiological methods, provides the definite diagnosis of an invasive fungal infection, the combination of different diagnostic procedures, which include microbiological cultures, histological, serological and molecular methods like PCR together with the pattern of clinical presentation, may currently be the best strategy for the prompt diagnosis, initiation and monitoring of IFDs. Early start of antifungal therapy is mandatory, but clinical diagnostics often do not provide clear evidence of IFD. Integrated care pathways have been proposed for management and therapy of IFDs with either the diagnostic driven strategy using the preemptive antifungal therapy as opposed to the clinical or empirical driven strategy using the 'traditional' empirical antifungal therapy. Antifungal agents preferentially used for systemic therapy of invasive fungal infections are amphotericin B preparations, fluconazole, voriconazole, posaconazole, caspofungin, anidulafungin, micafungin, and most recently isavuconazole. Clinical decision making must consider licensing status, local experience and availability, pharmacological and economic aspects.

Pneumonia After Hematopoietic Stem Cell Transplantation

Pneumonia is the main cause of morbidity and mortality after hematopoietic stem cell transplantation. Two thirds of pneumonias observed after both autologous and allogeneic stem cell transplantations are of infectious origin, and coinfections are frequent. One third is due to noninfectious process, such as alveolar hemorrhage, alveolar proteinosis, or alloimmune pulmonary complications such as bronchiolitis obliterans or idiopathic interstitial pneumonitis. Most of these noninfectious complications may require treatment with corticosteroids which may be deleterious in infection. On the other hand, these complications either mimic or may be complicated with infections. Therefore, a precise diagnosis of pneumonia is of crucial importance to decide of the optimal treatment. CT scan is the best procedure for imaging of the lung. Although several indirect biomarkers, such as serum or plasma galactomannan or (1-3) β(beta)-G-glucan, can help in the etiological diagnosis, only direct invasive investigations provide the best chance to identify the cause(s) of pneumonia. Bronchoalveolar lavage (BAL) under fiberoptic bronchoscopy is the procedure of choice to identify the cause of pulmonary infection. It is safe and reproducible, and its diagnostic yield is around 50 % if the BAL fluid is processed at the laboratory according to a prespecified protocol established between the transplanter, the infectious diseases’ specialist, the pneumologist, and the laboratory, allowing the identification of the most likely hypotheses. Transbronchial biopsy does not provide significant additional information to BAL in most cases and more often complicates with bleeding and pneumothorax. In case of a noncontributory BAL, the decision to proceed to a second BAL, a transthoracic biopsy, or a surgical biopsy should be cautiously weighted in a multidisciplinary approach in regard to the benefits and risks of invasive procedures versus empirical treatment.

Review on fungal enzyme inhibitors – potential drug targets to manage human fungal infections

The potential applications of enzyme inhibitors for the management of invasive fungal infections are explored.

Polymerase chain reaction blood tests for the diagnosis of invasive aspergillosis in immunocompromised people

BACKGROUND

Invasive aspergillosis (IA) is the most common life-threatening opportunistic invasive mould infection in immunocompromised people. Early diagnosis of IA and prompt administration of appropriate antifungal treatment are critical to the survival of people with IA. Antifungal drugs can be given as prophylaxis or empirical therapy, instigated on the basis of a diagnostic strategy (the pre-emptive approach) or for treating established disease. Consequently there is an urgent need for research into both new diagnostic tools and drug treatment strategies. Newer methods such as polymerase chain reaction (PCR) to detect fungal nucleic acids are increasingly being investigated.

OBJECTIVES

To provide an overall summary of the diagnostic accuracy of PCR-based tests on blood specimens for the diagnosis of IA in immunocompromised people.

SEARCH METHODS

We searched MEDLINE (1946 to June 2015) and EMBASE (1980 to June 2015). We also searched LILACS, DARE, Health Technology Assessment, Web of Science and Scopus to June 2015. We checked the reference lists of all the studies identified by the above methods and contacted relevant authors and researchers in the field.

SELECTION CRITERIA

We included studies that: i) compared the results of blood PCR tests with the reference standard published by the European Organisation for Research and Treatment of Cancer/Mycoses Study Group (EORTC/MSG); ii) reported data on false-positive, true-positive, false-negative and true-negative results of the diagnostic tests under investigation separately; and iii) evaluated the test(s) prospectively in cohorts of people from a relevant clinical population, defined as a group of individuals at high risk for invasive aspergillosis. Case-control studies were excluded from the analysis.

DATA COLLECTION AND ANALYSIS

Authors independently assessed quality and extracted data. For PCR assays, we evaluated the requirement for either one or two consecutive samples to be positive for diagnostic accuracy. We investigated heterogeneity by subgroup analyses. We plotted estimates of sensitivity and specificity from each study in receiver operating characteristics (ROC) space and constructed forest plots for visual examination of variation in test accuracy. We performed meta-analyses using the bivariate model to produce summary estimates of sensitivity and specificity.

MAIN RESULTS

Eighteen primary studies, corresponding to 19 cohorts and 22 data sets, published between 2000 and 2013 were included in the meta-analyses, with a median prevalence of IA (proven or probable) of 12.0% (range 2.5 to 30.8 %). The majority of people had received chemotherapy for a haematological malignancy or had undergone a hematopoietic stem cell transplant. Several PCR techniques were used among the included studies. The sensitivity and specificity of PCR for the diagnosis of IA varied according to the interpretative criteria used to define a test as positive. The mean sensitivity and specificity were 80.5% (95% CI; 73.0 to 86.3) and 78.5% (67.8 to 86.4) for a single positive test result, and 58.0% (36.5 to 76.8) and 96.2% (89.6 to 98.6) for two consecutive positive test results.

AUTHORS' CONCLUSIONS

PCR shows moderate diagnostic accuracy when used as screening tests for IA in high-risk patient groups. Importantly the sensitivity of the test confers a high negative predictive value (NPV) such that a negative test allows the diagnosis to be excluded. Consecutive positives show good specificity in diagnosis of IA and could be used to trigger radiological and other investigations or for pre-emptive therapy in the absence of specific radiological signs when the clinical suspicion of infection is high. When a single PCR positive test is used as diagnostic criterion for IA in a population of 100 people with a disease prevalence of 13.0% (overall mean prevalence), three people with IA would be missed (sensitivity 80.5%, 19.5% false negatives), and 19 people would be unnecessarily treated or referred for further tests (specificity of 78.5%, 21.5% false positives). If we use the two positive test requirement in a population with the same disease prevalence, it would mean that six IA people would be missed (sensitivity 58.0%, 42.1% false negatives) and three people would be unnecessarily treated or referred for further tests (specificity of 96.2%, 3.8% false positives). Galactomannan and PCR have good NPV for excluding disease but the low prevalence of disease limits the ability to rule in a diagnosis. The biomarkers are detecting different aspects of disease and the combination of both together is likely to be more useful.

Polymerase chain reaction blood tests for the diagnosis of invasive aspergillosis in immunocompromised people

BACKGROUND

Invasive aspergillosis (IA) is the most common life-threatening opportunistic invasive mould infection in immunocompromised people. Early diagnosis of IA and prompt administration of appropriate antifungal treatment are critical to the survival of people with IA. Antifungal drugs can be given as prophylaxis or empirical therapy, instigated on the basis of a diagnostic strategy (the pre-emptive approach) or for treating established disease. Consequently there is an urgent need for research into both new diagnostic tools and drug treatment strategies. Newer methods such as polymerase chain reaction (PCR) to detect fungal nucleic acids are increasingly being investigated.

OBJECTIVES

To provide an overall summary of the diagnostic accuracy of PCR-based tests on blood specimens for the diagnosis of IA in immunocompromised people.

SEARCH METHODS

We searched MEDLINE (1946 to June 2015) and EMBASE (1980 to June 2015). We also searched LILACS, DARE, Health Technology Assessment, Web of Science and Scopus to June 2015. We checked the reference lists of all the studies identified by the above methods and contacted relevant authors and researchers in the field.

SELECTION CRITERIA

We included studies that: i) compared the results of blood PCR tests with the reference standard published by the European Organisation for Research and Treatment of Cancer/Mycoses Study Group (EORTC/MSG); ii) reported data on false-positive, true-positive, false-negative and true-negative results of the diagnostic tests under investigation separately; and iii) evaluated the test(s) prospectively in cohorts of people from a relevant clinical population, defined as a group of individuals at high risk for invasive aspergillosis. Case-control studies were excluded from the analysis.

DATA COLLECTION AND ANALYSIS

Authors independently assessed quality and extracted data. For PCR assays, we evaluated the requirement for either one or two consecutive samples to be positive for diagnostic accuracy. We investigated heterogeneity by subgroup analyses. We plotted estimates of sensitivity and specificity from each study in receiver operating characteristics (ROC) space and constructed forest plots for visual examination of variation in test accuracy. We performed meta-analyses using the bivariate model to produce summary estimates of sensitivity and specificity.

MAIN RESULTS

Eighteen primary studies, corresponding to 19 cohorts and 22 data sets, published between 2000 and 2013 were included in the meta-analyses, with a median prevalence of IA (proven or probable) of 12.0% (range 2.5 to 30.8 %). The majority of people had received chemotherapy for a haematological malignancy or had undergone a hematopoietic stem cell transplant. Several PCR techniques were used among the included studies. The sensitivity and specificity of PCR for the diagnosis of IA varied according to the interpretative criteria used to define a test as positive. The mean sensitivity and specificity were 80.5% (95% CI; 73.0 to 86.3) and 78.5% (67.8 to 86.4) for a single positive test result, and 58.0% (36.5 to 76.8) and 96.2% (89.6 to 98.6) for two consecutive positive test results.

AUTHORS' CONCLUSIONS

PCR shows moderate diagnostic accuracy when used as screening tests for IA in high-risk patient groups. Importantly the sensitivity of the test confers a high negative predictive value (NPV) such that a negative test allows the diagnosis to be excluded. Consecutive positives show good specificity in diagnosis of IA and could be used to trigger radiological and other investigations or for pre-emptive therapy in the absence of specific radiological signs when the clinical suspicion of infection is high. When a single PCR positive test is used as diagnostic criterion for IA in a population of 100 people with a disease prevalence of 13.0% (overall mean prevalence), three people with IA would be missed (sensitivity 80.5%, 19.5% false negatives), and 19 people would be unnecessarily treated or referred for further tests (specificity of 78.5%, 21.5% false negatives). If we use the two positive test requirement in a population with the same disease prevalence, it would mean that six IA people would be missed (sensitivity 58.0%, 42.1% false negatives) and three people would be unnecessarily treated or referred for further tests (specificity of 96.2%, 3.8% false negatives). Galactamannan and PCR have good NPV for excluding disease but the low prevalence of disease limits the ability to rule in a diagnosis. The biomarkers are detecting different aspects of disease and the combination of both together is likely to be more useful.

Biomarkers for invasive aspergillosis: the challenges continue

The incidence of invasive aspergillosis (IA), an opportunistic infection in immunocompromised individuals, is rising, but its early diagnosis remains challenging and treatment options are limited. Hence there is an urgent need to improve existing diagnostic procedures as well as develop novel approaches. The clinical usefulness of galactomannan and β-d-glucan, widely used assays detecting cell-wall antigens of Aspergillus, is unclear and depends on clinicians' awareness of their practical limitations. This leaves room for new methods that utilise genomic, proteomic and metabolomics approaches as well as novel detection procedures, for example point-of-care lateral-flow devices. Each of these strategies has its own limitations and it is likely that a combination of methods will be required to achieve optimal performance for the diagnosis of IA and subsequent appropriate patient management.

Novel and sensitive qPCR assays for the detection and identification of aspergillosis causing species

Despite concerted efforts, diagnosis of aspergillosis is still a great challenge to clinical microbiology laboratories. Along with the requirement for high sensitivity and specificity, species-specific identification is important. We developed rapid, sensitive and species-specific qPCR assays using the TaqMan technology for the detection and identification of Aspergillus fumigatus and Aspergillus terreus. The assays were designed to target orthologs of the Streptomyces factor C gene that are only found in a few species of filamentous fungi. Fungi acquired this gene through horizontal gene transfer and divergence of the gene allows identification of species. The assays have potential as a molecular diagnosis tool for the early detection of fungal infection caused by Aspergillus fumigatus and Aspergillus terreus, which merits future diagnostic studies. The assays were sensitive enough to detect a few genomic equivalents in blood samples.

Invasive fungal infections in acute leukemia

Invasive fungal infection (IFI) is among the leading causes for morbidity, mortality, and economic burden for patients with acute leukemia. In the past few decades, the incidence of IFI has increased dramatically. The certainty of diagnosis of IFI is based on host factors, clinical evidence, and microbiological examination. Advancement in molecular diagnostic modalities (e.g. non-culture-based serum biomarkers such as β-glucan or galactomannan assays) and high-resolution radiological imaging has improved our diagnostic approach. The early use of these diagnostic tests assists in the early initiation of preemptive therapy. Nonetheless, the complexity of IFI in patients with leukemia and the limitations of these diagnostic tools still mandate astute clinical acumen. Its management has been further complicated by the increasing frequency of infection by non-Aspergillus molds (e.g. zygomycosis) and the emergence of drug-resistant fungal pathogens. In addition, even though the antifungal armamentarium has expanded rapidly in the past few decades, the associated mortality remains high. The decision to initiate antifungal treatment and the choice of anti-fungal therapy requires careful consideration of several factors (e.g. risk stratification, local fungal epidemiologic patterns, concomitant comorbidities, drug-drug interactions, prior history of antifungal use, overall cost, and the pharmacologic profile of the antifungal agents). In order to optimize our diagnostic and therapeutic management of IFI in patients with acute leukemia, further basic research and clinical trials are desperately needed.

Overview of invasive fungal infections

The incidence of invasive fungal infections (IFIs) has seen a marked increase in the last two decades. This is especially evident among transplant recipients, patients suffering from AIDS, in addition to those in receipt of immunosuppressive therapy. Worryingly, this increased incidence includes infections caused by opportunistic fungi and emerging fungal infections which are resistant to or certainly less susceptible than others to standard antifungal agents. As a direct response to this phenomenon, there has been a resolute effort over the past several decades to improve early and accurate diagnosis and provide reliable screening protocols thereby promoting the administration of appropriate antifungal therapy for fungal infections. Early diagnosis and treatment with antifungal therapy are vital if a patient is to survive an IFI. Substantial advancements have been made with regard to both the diagnosis and subsequent treatment of an IFI. In parallel, stark changes in the epidemiological profile of these IFIs have similarly occurred, often in direct response the type of antifungal agent being administered. The effects of an IFI can be far reaching, ranging from increased morbidity and mortality to increased length hospital stays and economic burden.

Fungal infections: diagnostic problems and choice of therapy

Fungi are typically opportunistic pathogens. Formerly, limitations in diagnostic techniques explain why invasive fungal infections are usually detected in a late stage of their development. Therefore, traditional guidelines dictate antifungal treatment for all patients with persisting fever. This is not longer justifiable in view of the potential adverse events and the economical burden associated with the use of the new antifungal drugs in an era with improved diagnostic tools. Amphotericin B has been the drug of choice for invasive fungal infections for more than 30 years. Owing to nephrotoxicity, its use in neutropenic patients has been largely abandoned in favor of a lipid formulation of amphotericin B, of which only liposomal amphotericin B has been scientifically tested in the first-line treatment of aspergillosis. Azoles constitute an acceptable alternative to intravenous amphotericin B for many invasive fungal infections.

[Laboratory diagnosis of fungal infection diseases]

A number of newer diagnostic procedures have been developed over the last few years as alternatives to conventional microbiological methods to detect invasive fungal diseases (IFD). This text reviews the performance of alternative methods in clinical settings, and their accuracy compared with that of microscopical examination and microbiological cultures. Some newer techniques considered as complementary and experimental procedures are also reviewed. The text is divided into three sections, including Candida infections, aspergillosis and infections due to rare and emerging fungal species.

Fungal diagnostics in pneumonia

Fungal pneumonia is increasingly common, particularly in highly immunosuppressed patients, such as solid organ or hematopoietic stem cell transplant recipients, and the diagnosis is evolving. Although standard techniques such as microscopy and culture remain the mainstays of diagnosis, relatively recent advances in serological and molecular testing are important additions to the field. This article reviews the laboratory tools used to diagnose fungal respiratory disease.

Evaluation of PCR on bronchoalveolar lavage fluid for diagnosis of invasive aspergillosis: a bivariate metaanalysis and systematic review

Background

Nucleic acid detection by polymerase chain reaction (PCR) is emerging as a sensitive and rapid diagnostic tool. PCR assays on serum have the potential to be a practical diagnostic tool. However, PCR on bronchoalveolar lavage fluid (BALF) has not been well established. We performed a systematic review of published studies to evaluate the diagnostic accuracy of PCR assays on BALF for invasive aspergillosis (IA).

Methods

Relevant published studies were shortlisted to evaluate the quality of their methodologies. A bivariate regression approach was used to calculate pooled values of the method sensitivity, specificity, and positive and negative likelihood ratios. Hierarchical summary receiver operating characteristic curves were used to summarize overall performance. We calculated the post-test probability to evaluate clinical usefulness. Potential heterogeneity among studies was explored by subgroup analyses.

Results

Seventeen studies comprising 1191 at-risk patients were selected. The summary estimates of the BALF-PCR assay for proven and probable IA were as follows: sensitivity, 0.91 (95% confidence interval (CI), 0.79–0.96); specificity, 0.92 (95% CI, 0.87–0.96); positive likelihood ratio, 11.90 (95% CI, 6.80–20.80); and negative likelihood ratio, 0.10 (95% CI, 0.04–0.24). Subgroup analyses showed that the performance of the PCR assay was influenced by PCR assay methodology, primer design and the methods of cell wall disruption and DNA extraction.

Conclusions

PCR assay on BALF is highly accurate for diagnosing IA in immunocompromised patients and is likely to be a useful diagnostic tool. However, further efforts towards devising a standard protocol are needed to enable formal validation of BALF-PCR.

Universal antifungal therapy is not needed in persistent febrile neutropenia: a tailored diagnostic and therapeutic approach

BACKGROUND

Giving antifungal therapy exclusively to selected patients with persistent febrile neutropenia may avoid over-treatment without increasing mortality. The aim of this study was to validate an innovative diagnostic and therapeutic approach based on assessing patients' risk profile and clinical criteria in order to select those patients requiring antifungal therapy. The efficacy of this approach was compared to that of universal empirical antifungal therapy.

DESIGN AND METHODS

This was a prospective study which included all consecutive adult hematology patients with neutropenia and fever refractory to 5 days of empirical antibacterial therapy admitted to a teaching hospital in Spain over a 2-year period. A diagnostic and therapeutic approach based on clinical criteria and risk profile was applied in order to select patients for antifungal therapy. The sensitivity, specificity and negative predictive value of this approach and also the overall success rate, according to the same criteria of efficacy described in classical clinical trials, were analyzed.

RESULTS

Eighty-five episodes were included, 35 of them (41.2%) in patients at high risk of invasive fungal infections. Antifungal therapy was not indicated in 33 episodes (38.8%). The overall incidence of proven and probable invasive fungal infections was 14.1%, all of which occurred in patients who had received empirical antifungal therapy. The 30-day crude mortality rate was 15.3% and the invasive fungal infection-related mortality rate was 2.8% (2/72). The overall success rate following the diagnostic and therapeutic approach was 36.5% compared with 33.9% and 33.7% obtained in the trial by Walsh et al. The sensitivity, specificity and negative predictive value of the study approach were 100%, 52.4% and 100%, respectively.

CONCLUSIONS

Based on the high negative predictive value of this diagnostic and therapeutic approach in persistent febrile neutropenia patients with hematologic malignancies or patients who have received a hematopoietic stem cell transplant, the approach is useful for identifying patients who are not likely to develop invasive fungal infection and do not, therefore, require antifungal therapy. The effectiveness of the strategy is similar to that of universal empirical antifungal therapy reported in controlled trials.

Diagnosis of invasive aspergillosis by a commercial real-time PCR assay for Aspergillus DNA in bronchoalveolar lavage fluid samples from high-risk patients compared to a galactomannan enzyme immunoassay

Culture-independent molecular techniques such as real-time PCRs offer the potential for early diagnosis of invasive aspergillosis (IA), thereby reducing the disease-associated mortality rate. PCR-based testing is presently excluded from disease-defining consensus criteria due to lack of standardization and clinical validation. A single-center prospective study was conducted to investigate the performance of the commercially available MycAssay Aspergillus test for detecting Aspergillus DNA in patients with suspicion of IA. To this end, a total of 158 bronchoalveolar lavage (BAL) fluid specimens that were consecutively collected from hematology (n = 68) and intensive care unit (n = 90) patients were examined. Sixteen of 17 (94.1%) specimens from patients with proven/probable IA were MycAssay positive, and 15 of these 16 patients were also positive by an "in-house" PCR assay. A total of 139 of 141 (98.6%) specimens from patients without proven/probable IA were MycAssay negative. Fifteen of 16 (94.1%) MycAssay-positive patients were also positive for BAL fluid galactomannan (GM) at an index cutoff of ≥1.0 (index range, 1.1 to 8.3), as were 3 patients without IA but with pulmonary fusariosis. Interestingly, in seven of the PCR-positive BAL specimens that tested culture positive for Aspergillus species, cycle threshold values were earlier than those of specimens with a culture-negative result. In conclusion, the MycAssay Aspergillus PCR appears to be a sensitive and specific molecular test for the diagnosis of IA, and its performance is comparable to that of the GM assay. However, more large studies are necessary to firmly establish its clinical utility in high-risk settings.

Diagnosis of invasive fungal infections in hematology and oncology--guidelines from the Infectious Diseases Working Party in Haematology and Oncology of the German Society for Haematology and Oncology (AGIHO)

Invasive fungal infections (IFIs) are a primary cause of morbidity and mortality in patients with hematological malignancies. Establishing a definite diagnosis of IFI in immunocompromised patients is particularly challenging and time consuming, but delayed initiation of antifungal treatment increases mortality. The limited overall outcome has led to the strategy of initiating either 'empirical' or 'preemptive' antifungal therapy before the final diagnosis. However, diagnostic procedures have been vastly improved in recent years. Particularly noteworthy is the introduction of newer imaging techniques and non-culture methods, including antigen-based assays, metabolite detection and molecular detection of fungal DNA from body fluid samples. Though varying widely in cancer patients, the risk of IFI is highest in those with allogeneic stem cell transplantation and those with acute leukemia. The AGIHO presents recommendations for the diagnosis of IFIs with risk-adapted screening concepts for febrile episodes in patients with haemato-oncological disorders.

Design issues in a randomized controlled trial of a pre-emptive versus empiric antifungal strategy for invasive aspergillosis in patients with high-risk hematologic malignancies

Invasive aspergillosis (IA) is a major cause of mortality in patients with hematological malignancies, due largely to the inability of traditional culture and biopsy methods to make an early or accurate diagnosis. Diagnostic accuracy studies suggest that Aspergillus galactomannan (GM) enzyme immunoassay (ELISA) and Aspergillus PCR-based methods may overcome these limitations, but their impact on patient outcomes should be evaluated in a diagnostic randomized controlled trial (D-RCT). This article describes the methodology of a D-RCT which compares a new pre-emptive strategy (GM-ELISA- and Aspergillus PCR-driven antifungal therapy) with the standard fever-driven empiric antifungal treatment strategy. Issues including primary end-point and patient selection, duration of screening, choice of tests for the pre-emptive strategy, antifungal prophylaxis and bias control, which were considered in the design of the trial, are discussed. We suggest that the template presented herein is considered by researchers when evaluating the utility of new diagnostic tests (ClinicalTrials.gov number, NCT00163722).

Antifungal treatment strategies in patients with haematological diseases or cancer: from prophylaxis to empirical, pre-emptive and targeted therapy

Immunocompromised patients have a high risk for invasive fungal diseases (IFDs). These infections are mostly life-threatening and an early diagnosis and initiation of appropriate antifungal therapy are essential for the clinical outcome. Empirical treatment is regarded as the standard of care for granulocytopenic patients who remain febrile despite broad-spectrum antibiotics. However, this strategy can bear a risk of overtreatment and subsequently induce toxicities and unnecessary treatment costs. Pre-emptive antifungal therapy is now increasingly used to close the time gap between delayed initiation for proven disease and empirical treatment for anticipated infection without further laboratory or radiological evidence of fungal disease. Currently, some new non-invasive microbiological and laboratory methods, like the Aspergillus-galactomannan sandwich-enzyme immunoassay (Aspergillus GM-ELISA), 1,3-β-D-glucan assay or PCR techniques have been developed for a better diagnosis and determination of target patients. The current diagnostic approaches to fungal infections and the role of the revised definitions for invasive fungal infections, now IFDs, will be discussed in this review as well as old and emerging approaches to empirical, pre-emptive and targeted antifungal therapies in patients with haemato-oncological malignancies.

Evaluation of analytical and preliminary clinical performance of Myconostica MycAssay Aspergillus when testing serum specimens for diagnosis of invasive Aspergillosis

Diagnosis of invasive aspergillosis remains a significant problem. PCR testing may aid diagnosis but is not yet included in disease-defining criteria due to a lack of standardization of assays and methodologies. This study investigated the analytical performance and the clinical sensitivity and specificity of the Myconostica MycAssay Aspergillus PCR (MAP) assay compared to those of a validated in-house Aspergillus PCR (IHP) test when testing serum specimens. Serum specimens spiked with Aspergillus genomic DNA had a limit of detection equivalent to 5 genomes and a linear dynamic range of 5 to >5 × 10(4) genomes for both assays. When testing clinical specimens (n = 170), the MAP assay had a sensitivity of 60 to 70% and a specificity of 90.5 to 100%. The IHP assay had a sensitivity of 50 to 80% and a specificity of 100%. A commercially available Aspergillus PCR assay provides a methodology that is standardized and reagents that are quality controlled. This facilitates multicenter evaluation of the clinical utility of PCR diagnosis. The performance of the MAP assay is comparable to that of the IHP assay and to those in previously reported studies evaluating commercial tests (galactomannan enzyme-linked immunosorbent assay).

Risk factors associated with invasive fungal disease in children with cancer and febrile neutropenia: a prospective multicenter evaluation

BACKGROUND

Empiric antifungal treatment has become standard of care in children with cancer and prolonged fever and febrile neutropenia (FN), with the downside that it leads to significant over treatment. We characterized epidemiologic, clinical, and laboratory features of invasive fungal disease (IFD) in children with cancer and FN with the aim to identify risk factors for IFD that can aid in better selecting children who require antifungal treatment.

METHODS

In a prospective, multicenter study, children admitted with FN at high-risk for sepsis, in 6 hospitals in Santiago, Chile were monitored from admission until the end of the FN episode. Monitoring included periodic evaluation of clinical findings, absolute neutrophil count, absolute monocyte count (AMC), serum C-reactive protein (CRP), bacterial cultures, imaging studies, and galactomannan antigen. A diagnosis of proven, probable, and possible IFD was made after episode resolution based on European Organization for Research and Treatment of Cancer classification.

RESULTS

A total of 646 high-risk FN episodes were admitted during the study period, of which 604 were enrolled. IFD was diagnosed in 35 episodes (5.8%) of which 7 (1.2%) were proven, 10 (1.6%) probable, and 18 (3.0%) possible. Four variables obtained on day 4 were significantly more common in IFD cases, which were presence of fever, absolute neutrophil count < or =500/mm, AMC < or =100/mm, and CRP > or =90 mg/L. The combination of fever, AMC < or =100/mm, and CRP > or =90 at day 4 provided a RR for IFD of 5.4 (99% CI, 3.2-9.2) with a sensitivity of 75%, specificity of 87%, positive and negative predictive values of 13% and 99%, respectively.

CONCLUSIONS

Fever persisting at day 4 of admission, together with AMC < or =100 and CRP > or =90 significantly increased the risk for IFD in children with cancer.

Early Diagnosis of Invasive Aspergillosis in Neutropenic Patients. Comparison between Serum Galactomannan and Polymerase Chain Reaction

Background:

Invasive aspergillosis (IA) is a major cause of morbidity and mortality in profoundly neutropenic patients, so early diagnosis is mandatory.

Aim:

Consecutive patients with hematological malignancies undergoing intensive chemotherapy were screened for IA with two different methods which were compared.

Methods:

From October 2000 to August 2003 we tested 1311 serum samples from 172 consecutive patients with a polymerase chain reaction assay and between April 2005 and April 2008 we tested 806 serum samples from 169 consecutive patients with a Galactomannan (GM) test. Bronchoalveolar (BAL) samples were obtained whenever the patient’s condition allowed and tested with either method.

Results:

The serum PCR assay had a sensitivity of 75.0% and a specificity of 91.9% and the serum GM assay had a sensitivity of 87.5% and a specificity of 93.1%, (P > 0.05). The presence of two or more consecutive positive serum samples was predictive of IA for both assays. BAL GM/PCR was positive in some patients without serum positivity and in patients with 2 or more positive serum GM/PCR.

Conclusions:

No significant differences between the 2 serum tests were found. The GM assay has the advantage of being standardized among several laboratories and is incorporated in the criteria established by the European Organization for Research and Treatment of Cancer/Invasive Fungal Infections Cooperative Group and the National Institute of Allergy and Infectious Diseases Mycosis Study Group (EORTC/MSG), however is much more expensive. BAL GM and PCR sampling aids in IA diagnosis but needs further validation studies to differentiate between colonization and true infection in cases where serum GM or PCR are negative.

Therapeutic impact and diagnostic performance of multiplex PCR in patients with malignancies and suspected sepsis

OBJECTIVES

New molecular methods allow rapid pathogen detection in patients with sepsis, but their impact on treatment decisions remains to be established. We evaluated the therapeutic usefulness of multiplex PCR testing in patients with cancer and sepsis.

METHODS

110 patients with cancer and sepsis were included prospectively and underwent LightCycler® SeptiFast (LC-SF) multiplex PCR testing in addition to standard tests. Two independent panels of experts assessed the diagnosis in each patient based on medical record data; only one panel had the LC-SF results. The final diagnosis established by a third panel was the reference standard.

RESULTS

The final diagnosis was documented sepsis in 50 patients (55 microorganisms), undocumented sepsis in 54, and non-infectious disease in 6. LC-SF detected 17/32 pathogens recovered from blood cultures (BC) and 11/23 pathogens not recovered from BC; 12 microorganisms were detected neither by BC nor by LC-SF. LC-SF produced false-positive results in 10 cases. The LC-SF results would have significantly improved treatment in 11 (10%) patients and prompted immediate antimicrobial therapy not given initially in 3 patients.

CONCLUSIONS

In cancer patients with suspected sepsis, LC-SF detected 11/55 (20%) true pathogens not recovered from BCs and would have improved the initial management in 11/110 (10%) patients.

Aspergillus PCR: one step closer to standardization

PCR has been used as an aid in the diagnosis of invasive aspergillosis for almost 2 decades. A lack of standardization has limited both its acceptance as a diagnostic tool and multicenter clinical evaluations, preventing its inclusion in disease-defining criteria. In 2006, the European Aspergillus PCR Initiative was formed. The aim of the initiative was to provide optimal standardized protocols for the widespread clinical evaluation of the Aspergillus PCR to determine its diagnostic role and allow inclusion in disease diagnosis criteria. Quality control panels were developed and circulated to centers for evaluation of the existing methodology before recommendations based on the initial results were proposed for further panels. The centers were anonymously classified as "compliant" or "noncompliant," according to whether they had followed the proposed recommendations before the performance parameters were determined and meta-regression analysis was performed. Most PCR amplification systems provided similar detection thresholds, although positivity was a function of the fungal burden. When PCR amplification was combined with DNA extraction, 50% of the centers failed to achieve the same level of detection. Meta-regression analysis showed positive correlations between sensitivity and extraction protocols incorporating the proposed recommendations and the use of bead beating, white cell lysis buffer, and an internal control PCR. The use of elution volumes above 100 microl showed a negative correlation with sensitivity. The efficiency of the Aspergillus PCR is limited by the extraction procedure and not by PCR amplification. For PCR testing of whole blood, it is essential that large blood volumes (>or=3 ml) be efficiently lysed before bead beating to disrupt the fungal cell and performance of an internal control PCR to exclude false negativity. DNA should be eluted in volumes of <100 microl.

Prospective monitoring for invasive aspergillosis using galactomannan and polymerase chain reaction in high risk pediatric patients

BACKGROUND

The diagnosis of invasive aspergillus remains a challenge in the care of high-risk patients. Outcomes are improved when invasive aspergillus is diagnosed early, prompting the initiation of appropriate antifungal therapy. We evaluated the utility of prospective monitoring for invasive aspergillosis (IA) using biomarkers such as serum galactomannan (GM) and/or blood polymerase chain reaction (PCR) in high-risk pediatric patients.

METHODS

Patients with high-risk leukemia (HRL) or allogenic hematopoietic cell transplant (HCT) recipients were prospectively monitored twice weekly for IA using GM and PCR for Aspergillus species.

RESULTS

Sixty-eight patients had collected >or=2 specimens. The 1086 specimens were collected; 627 from HRL (58%) and 459 (42%) from HCT recipients. Median specimens/patient was 11.0 (2 to 58), and median follow-up/patient was 98.5 days (14 to 437). Fifty-six percent of samples were obtained from patients receiving mold-active agents; 32% HRL and 89% HCT. There were no proven, 3 probable, and 20 possible episodes of IA. Thirteen specimens (1.2%) from 4 patients (5%) were GM+. None were positive by PCR.

CONCLUSIONS

The prospective use of GM and PCR in this high-risk pediatric population did not identify cases of proven IA. A high false positive rate was not detected. It is speculated that changes in clinical practice, such as early use of empiric and/or prophylactic mold-active agent and frequent imaging studies have impacted the epidemiology of IA. In a population with low incidence of IA, the use of these assays as a screening device on blood may not further enhance current outcomes.

[Current status of invasive fungal infections. New diagnostic techniques and antifungal agents]

In the last few years, major advances in the treatment of transplant recipients, with hemato-oncological diseases or admitted to the intensive care unit, has been accompanied by an increase in classical fungal infections and by the emergence of uncommon fungal infections. Despite the development of new diagnostic techniques such as galactomannan detection and the availability of new antifungal agents, these opportunistic infections continue to pose a diagnostic challenge, prolong length of hospital stay, and increase costs. In addition, mortality from these infections is high. The present chapter provides a brief review of the epidemiology of these infections, diagnostic advances, and the new antifungal agents that have been developed in the last few years.

Surgical management of invasive pulmonary fungal infection in hematology patients

BACKGROUND

The purpose of this study was to analyze our institutional results with pulmonary resection in neutropenic patients with hematologic malignancies and suspected invasive pulmonary fungal infections.

METHODS

We performed a retrospective medical record review of 25 immunocompromised patients with hematologic malignancies who underwent pulmonary resection between 2000 and 2007. We analyzed preoperative diagnostic technique, degree of pulmonary resection, and postoperative morbidity and mortality to determine whether surgery is a viable treatment option in this subset of patients.

RESULTS

Twenty-three of 25 patients had a minithoracotomy compared with 2 who had video-assisted thorascopic surgery resection only. Thirteen had wedge resections, 9 had lobectomies, and 3 had segmentectomies. Early surgical morbidity was 2 of 25, involving 1 pneumothorax and 1 empyema. In-hospital mortality was 2, with 1 death primarily related to surgery. Median survival was 342 days, and survival was significantly better in patients with only one lesion. No patient experienced late recurrence of invasive pulmonary fungal infection. Resected pulmonary tissue also provided the best chance for a proven diagnosis in 19 of 25 (76%).

CONCLUSIONS

This study confirms that pulmonary resection in high-risk immunocompromised patients with suspected invasive fungal infection can be carried out with excellent operative morbidity and mortality.

Use of PCR for diagnosis of invasive aspergillosis: systematic review and meta-analysis

A systematic review and meta-analysis was done on the use of PCR tests for the diagnosis of invasive aspergillosis. Data from more than 10000 blood, serum, or plasma samples obtained from 1618 patients at risk for invasive aspergillosis were retrieved from 16 studies. Overall, the mean diagnostic odds ratios (DORs) of PCR for proven and probable cases were similar whether two consecutive positive samples were required to define positivity (DOR 15.97 [95% CI 6.83-37.34]) or a single positive PCR test was required (DOR 16.41 [95% CI 6.43-41.88]). Sensitivity and specificity of PCR for two consecutive positive samples were 0.75 (95% CI 0.54-0.88) and 0.87 (95% CI 0.78-0.93), respectively, and if only a single positive sample was required, these values were 0.88 (95% CI 0.75-0.94) and 0.75 (95% CI 0.63-0.84), respectively. Whereas specificity based on a single positive test was significantly lower (p=0.027) than two positive tests, the sensitivity and DOR did not differ significantly. A single PCR-negative result is thus sufficient to exclude a diagnosis of proven or probable invasive aspergillosis. However, two positive tests are required to confirm the diagnosis because the specificity is higher than that attained from a single positive test. Populations at risk varied and there was a lack of homogeneity of the PCR methods used. Efforts are underway to devise a standard for Aspergillus sp PCR for screening, which will help enable formal validation of PCR and estimate its use in patients most likely to benefit.

The utility of a nebulised intra-tracheal rat model of invasive pulmonary aspergillosis

Invasive pulmonary aspergillosis (IPA) is of particular concern to immunodeficient patients, whose mortality rates may exceed 80%. The development of an animal model that faithfully reproduces the pathophysiology of IPA would improve the studies on diagnostic and therapeutic modes, and the use of rats as a possible model for IPA seems to have been largely overlooked. Such a model could be established with the MicroSprayer IA-1B. Male Sprague-Dawley rats (6-8 weeks old) were rendered immunodeficient by cyclophosphamide injections and a protein-deficient diet. On day D0, they were anaesthetised by inhalation of 5% isoflurane and infected by the intra-tracheal aerosolization of 100 microl of an Aspergillus fumigatus spore suspension through a MicroSprayer IA-1B. This inoculation process was simple and rapid, with no deaths observed during or immediately after the procedure. The rats regained consciousness within 1 min. Follow-up data including those for clinical factors (weight changes, mortality rate), biological factors (Aspergillus antigens) and histological factors were consistent with previous studies. The advantages of this model include the ease of animal manipulation, the reproducibility of infection and the potential for repeated blood sampling.

Risk stratification for invasive aspergillosis: early assessment of host susceptibility

Outcomes of invasive aspergillosis are substantially improved with early initiation of therapy. Unfortunately, the diagnosis remains difficult to establish so that early suspicion of infection is imperative. Identification of high risk patients and use of non-culture-based diagnostics and radiographic studies can facilitate earlier recognition of infection. It is important to realize that the timing and spectrum of risk for invasive aspergillosis have expanded. While patients with hematological malignancies and hematopoietic stem cell transplants make up the highest risk groups, patients such as those receiving steroids and other immunosuppressive therapies are also at risk. Non-culture-based methods (including galactomannan, 1,3-beta-D-glucan, and PCR-based methods) are actively being pursued to improve early diagnosis. Thus, identifying patients at high risk for infection and utilizing non-culture-based methods and radiologic studies to assist in establishing a likely diagnosis of invasive aspergillosis will further enhance the role of new agents in the early, effective treatment and prophylaxis of invasive aspergillosis.