Galactomannan Enzyme-linked Immunosorbent Assay Research Articles

Performance of the JF5-Based Galactomannoprotein EIA Compared to the Lateral Flow Device and the Galactomannan EIA in Serum and Bronchoalveolar Lavage Fluid.

Early diagnosis of invasive aspergillosis is an important factor to improve survival but remains challenging. The detection of Aspergillus antigens is included in the consensus case definitions of the European Organization for Research and Treatment of Cancer and the National Institute of Allergy and Infectious Diseases Mycoses Study Group as a criterion of "probable" invasive aspergillosis. JF5, a mouse IgG3 monoclonal antibody detecting an Aspergillus mannoprotein, has already been implemented as a lateral flow device (LFD). Now, also a JF5-based enzyme-linked immunosorbent assay (EIA) is commercialized (Aspergillus specific galactomannoprotein [GP] EIA, Euroimmun Medizinische Labordiagnostika AG). In this study, we analyzed the diagnostic performance of GP in 63 bronchoalveolar lavage fluid (BALf) samples and 224 serum samples and compared it to performance of the galactomannan (GM) (Platelia Aspergillus enzyme immunoassay (EIA) (Bio-Rad, Marnes-la-Coquette, France)) and the JF5-based LFD (AspLFD; OLM Diagnostics, Newcastle Upon Tyne, United Kingdom). The diagnostic performance of GP and GM correlated well with both having high specificity. With an optimized cutoff threshold for positivity of 0.4-deviating from the 0.5 threshold recommended by the manufacturer-sensitivity of GP in serum is not significantly different than that of GM. However, in BALf sensitivity of GP is significantly less than for GM.

Evaluation of Aspergillus Galactomannan Lateral Flow Assay on Serum and Bronchoalveolar Lavage Specimens

Background: Detection of biomarkers, such as galactomannan (GM), has proven to be of great significance in early recognition of invasive aspergillosis (IA). The aim of our study was to evaluate the lateral flow assay (LFA) for the detection of GM on serum and bronchoalveolar lavage (BAL) samples previously proven positive by enzyme-linked immunosorbent assay (ELISA). Methods: The study was performed on serum and BAL samples obtained from patients with suspected IA in the period from February 2019 to January 2020, which were previously GM positive by ELISA (Platelia Aspergillus Ag, Biorad, Hercules, USA). Samples were then tested by LFA (Aspergillus Galactomannan LFA, IMMY, Oklahoma, USA) with test line intensity visually read as 1+, 2+, 3+, or 4+. Results: A total of 45 GM ELISA positive serum and/or BAL samples were obtained from 41 patients; 25 (55,6 %) were BAL and 20 (44,4 %) serum samples. LFA showed a positive result in 39 out of 45 (86,7%) GM ELISA positive samples; 22/25 (88.0 %) BAL samples and 17/20 (85.0 %) serum samples tested positive. In BAL samples, low intensity test line of 1+ was significantly more frequent in GM ELISA positive samples with optical density index (ODI) < 1.0 (p=0.0002). Three serum samples with high GM ELISA ODI (>4.0) had low intensity line of 1+ when tested with LFA. Conclusions: Results obtained by LFA are comparable to GM ELISA. Since low intensity lines were found in serum samples with high ODI, this potentially makes BAL a superior sample for LFA, at least when visual and not automated reading is done.

Combining urine antigen and blood polymerase chain reaction for the diagnosis of disseminated histoplasmosis in hospitalized patients with advanced HIV disease.

In this prospective cohort study carried-out in a referral center in São Paulo, Brazil, we found a high frequency of AIDS-related disseminated histoplasmosis (8/106, 7.5%). We used urine antigen test and blood PCR assay to improve the diagnosis of this opportunistic disease.

An Evaluation of the Performance of the IMMY Aspergillus Galactomannan Enzyme-Linked Immunosorbent Assay When Testing Serum To Aid in the Diagnosis of Invasive Aspergillosis.

The objectives of this study were to evaluate the performance of the recently released IMMY Aspergillus galactomannan enzyme immunoassay (IMMY GM-EIA) when testing serum samples and to identify the optimal galactomannan index (GMI) positivity threshold for the diagnosis of invasive aspergillosis (IA). This was a retrospective case/control study, comprising 175 serum samples obtained from 131 patients, 35 of whom had probable or possible invasive fungal disease (IFD) as categorized using recently revised, internationally accepted definitions. The IMMY GM-EIA was performed following the manufacturer's instructions. Performance parameters were determined and receiver operator characteristic analysis was used to identify an optimal GMI threshold. Concordance with the Bio-Rad Aspergillus Ag assay (Bio Rad GM-EIA) and IMMY sona Aspergillus lateral flow assay was assessed. The median GMIs generated by the IMMY GM-EIA for samples originating from probable IA/IFD cases (n = 31), possible IFD (n = 4), and control patients (n = 100) were 0.61, 0.11, and 0.14, respectively, and were comparable to those of the Bio-Rad GM-EIA (0.70, 0.04, and 0.04, respectively). Overall qualitative observed sample agreement between the IMMY GM-EIA and Bio-Rad GM-EIA was 94.7%, generating a kappa statistic of 0.820. At a GMI positivity threshold of ≥0.5, the IMMY GM-EIA had a sensitivity and specificity of 71% and 98%, respectively. Reducing the threshold to ≥0.27 generated sensitivity and specificity of 90% and 92%, respectively. The IMMY GM-EIA provides a comparable alternative to the Bio-Rad GM-EIA when testing serum samples. Further prospective, multicenter evaluations are required to confirm the optimal threshold and associated clinical performance.

The screening of blood by Aspergillus PCR and galactomannan ELISA precedes BAL detection in patients with proven and probable IA.

Early detection of Aspergillus infection has the potential to facilitate a more effective management of invasive disease. Data from probable/proven cases of invasive aspergillosis (IA) with a positive galactomannan enzyme-linked immunosorbent assay (GM) bronchoalveolar lavage fluid (BALF) was analyzed in respect to serum GM and/or polymerase chain reaction (PCR) screening of blood samples prior to, or concurrent with bronchoscopy. Concurrent serum GM testing is less sensitive than BALF itself. Nevertheless screening of blood using GM or PCR testing detected IA cases earlier (GM: 42% or PCR: 56%), particularly when combined (GM/PCR: 73%). Therefore, regular screening facilitates and improves early detection of IA in patients suffering from acute leukemia.

Higher frequency of false-positive serum galactomannan tests among older subjects and the association with elevated serum immunoglobulin G levels.

The incidence of false-positive serum galactomannan (GM) enzyme-linked immunosorbent assay test results has been scarcely examined among older subjects. Additionally, previous studies have highlighted the influence of serum immunoglobulin G (IgG) levels on GM test results. We hypothesised that age-related IgG level elevation might also be associated with false-positive GM test results in older subjects. This study aimed to examine the association between false-positive GM test results and age or serum IgG levels. We investigated the association between false-positive serum GM test results and age in 1071 healthy adult subjects. Then, we validated this association and further explored the correlation with serum IgG levels by retrospectively identifying 700 patients with newly diagnosed haematologic disorders without probable or proven invasive aspergillosis. Healthy subjects with false-positive GM test results were significantly older than those without false-positive results (P<0.001). Among patients with haematologic disorders, IgG myeloma patients showed significantly higher false-positive rates (57/125 [45.6%]) than patients with other haematologic disorders (non-Hodgkin lymphoma: 48/315 [15.2%], myelodysplastic syndrome/aplastic anaemia: 19/141 [13.5%]; both P<0.001) or other types of myeloma (IgA myeloma: 13/60 [21.7%], light chain myeloma: 9/52 [17.3%]; both P<0.01). Furthermore, among non-multiple myeloma patients, advanced age and higher IgG level were also significantly associated with the high frequency of false-positive GM test results. False-positive serum GM test results were frequent among older subjects and patients with elevated serum IgG levels. These results suggested that age- and/or disease-related IgG level elevation could induce this phenomenon.

Galactomannan detection in broncho-alveolar lavage fluid for invasive aspergillosis in immunocompromised patients.

Invasive aspergillosis (IA) is a life-threatening opportunistic mycosis that occurs in some people with a compromised immune system. The serum galactomannan enzyme-linked immunosorbent assay (ELISA) rapidly gained widespread acceptance as part of the diagnostic work-up of a patient suspected of IA. Due to its non-invasive nature, it can be used as a routine screening test. The ELISA can also be performed on bronchoalveolar lavage (BAL), allowing sampling of the immediate vicinity of the infection. The invasive nature of acquiring BAL, however, changes the role of the galactomannan test significantly, for example by precluding its use as a routine screening test. To assess the diagnostic accuracy of galactomannan detection in BAL for the diagnosis of IA in people who are immunocompromised, at different cut-off values for test positivity, in accordance with the Cochrane Diagnostic Test Accuracy Handbook. We searched three bibliographic databases including MEDLINE on 9 September 2016 for aspergillosis and galactomannan as text words and subject headings where appropriate. We checked reference lists of included studies for additional studies. We included cohort studies that examined the accuracy of BAL galactomannan for the diagnosis of IA in immunocompromised patients if they used the 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) classification as reference standard. Two review authors assessed study quality and extracted data. Quality Assessment of Diagnostic Accuracy Studies-2 (QUADAS-2) was used for quality assessment. We included 17 studies in our review. All studies except one had a high risk of bias in two or more domains. The diagnostic performance of an optical density index (ODI) of 0.5 as cut-off value was reported in 12 studies (with 1123 patients). The estimated sensitivity was 0.88 (95% confidence interval (CI) 0.75 to 1.00) and specificity 0.81 (95% CI 0.71 to 0.91). The performance of an ODI of 1.0 as cut-off value could be determined in 11 studies (with 648 patients). The sensitivity was 0.78 (95% CI 0.61 to 0.95) and specificity 0.93 (95% CI 0.87 to 0.98). At a cut-off ODI of 1.5 or higher, the heterogeneity in specificity decreased significantly and was invariably >90%. The optimal cut-off value depends on the local incidence and clinical pathway. At a prevalence of 12% a hypothetical population of 1000 patients will consist of 120 patients with IA. At a cut-off value of 0.5 14 patients with IA will be missed and there will be 167 patients incorrectly diagnosed with IA. If we use the test at a cut-off value of 1.0, we will miss 26 patients with IA. And there will be 62 patients incorrectly diagnosed with invasive aspergillosis. The populations and results were very heterogeneous. Therefore, interpretation and extrapolation of these results has to be performed with caution. A test result of 1.5 ODI or higher appears a strong indicator of IA.

Multicenter Validation of Commercial Antigenuria Reagents To Diagnose Progressive Disseminated Histoplasmosis in People Living with HIV/AIDS in Two Latin American Countries.

Histoplasmosis is an important cause of mortality in patients with AIDS, especially in countries with limited access to antiretroviral therapies and diagnostic tests. However, many disseminated infections in Latin America go undiagnosed. A simple, rapid method to detect Histoplasma capsulatum infection in regions where histoplasmosis is endemic would dramatically decrease the time to diagnosis and treatment, reducing morbidity and mortality. The aim of this study was to validate a commercial monoclonal Histoplasma galactomannan (HGM) enzyme-linked immunosorbent assay (Immuno-Mycologics [IMMY], Norman, OK, USA) in two cohorts of people living with HIV/AIDS (PLHIV). We analyzed urine samples from 589 people (466 from Guatemala and 123 from Colombia), including 546 from PLHIV and 43 from non-PLHIV controls. Sixty-three of these people (35 from Guatemala and 28 from Colombia) had confirmed histoplasmosis by isolation of H. capsulatum Using the standard curve provided by the quantitative commercial test, the sensitivity was 98% (95% confidence interval [CI], 95 to 100%) and the specificity was 97% (95% CI, 96 to 99%) (cutoff = 0.5 ng/ml). Semiquantitative results, using a calibrator of 12.5 ng/ml of Histoplasma galactomannan to calculate an enzyme immunoassay index value (EIV) for the samples, showed a sensitivity of 95% (95% CI, 89 to 100%) and a specificity of 98% (95% CI, 96 to 99%) (cutoff ≥ 2.6 EIV). This relatively simple-to-perform commercial antigenuria test showed a high performance with reproducible results in both countries, suggesting that it can be used to detect progressive disseminated histoplasmosis in PLHIV in a wide range of clinical laboratories in countries where histoplasmosis is endemic.

Galactomannan detection for invasive aspergillosis in immunocompromised patients.

Invasive aspergillosis is the most common life-threatening opportunistic invasive mycosis in immunocompromised patients. A test for invasive aspergillosis should neither be too invasive nor too great a burden for the already weakened patient. The serum galactomannan enzyme-linked immunosorbent assay (ELISA) seems to have the potential to meet both requirements. To obtain summary estimates of the diagnostic accuracy of galactomannan detection in serum for the diagnosis of invasive aspergillosis. We searched MEDLINE, EMBASE and Web of Science with both MeSH terms and text words for both aspergillosis and the sandwich ELISA. We checked the reference lists of included studies and review articles for additional studies. We conducted the searches in February 2014. We included cross-sectional studies, case-control designs and consecutive series of patients assessing the diagnostic accuracy of galactomannan detection for the diagnosis of invasive aspergillosis in patients with neutropenia or patients whose neutrophils are functionally compromised. The reference standard was composed of the criteria given by the European Organization for Research and Treatment of Cancer (EORTC) and the Mycoses Study Group (MSG). Two review authors independently assessed quality and extracted data. We carried out meta-analysis using the bivariate method. We investigated sources of heterogeneity by adding potential sources of heterogeneity to the model as covariates. We included 54 studies in the review (50 in the meta-analyses), containing 5660 patients, of whom 586 had proven or probable invasive aspergillosis. When using an optical density index (ODI) of 0.5 as a cut-off value, the sensitivity of the test was 82% (73% to 90%) and the specificity was 81% (72% to 90%). At a cut-off value of 1.0 ODI, the sensitivity was 72% (65% to 80%) and the specificity was 88% (84% to 92%). At a cut-off value of 1.5 ODI, the sensitivity was 61% (47% to 75%) and the specificity was 93% (89% to 97%). None of the potential sources of heterogeneity had a statistically significant effect on either sensitivity or specificity. If we used the test at a cut-off value of 0.5 ODI in a population of 100 patients with a disease prevalence of 9% (overall median prevalence), two patients who have invasive aspergillosis would be missed (sensitivity 82%, 18% false negatives), and 17 patients would be treated unnecessarily or referred unnecessarily for further testing (specificity 81%, 19% false negatives). If we used the test at a cut-off value of 1.5 in the same population, that would mean that four invasive aspergillosis patients would be missed (sensitivity 61%, 39% false negatives), and six patients would be treated or referred for further testing unnecessarily (specificity 93%, 7% false negatives). These numbers should, however, be interpreted with caution because the results were very heterogeneous.

PIN55 - Economic Analysis of Empiric Versus Diagnostic-Driven Strategies for Immunocompromised Patients With Suspected Aspergillus Invasive Fungal Infections In China

PIN55 EcoNomIc ANAlysIs of EmPIrIc VErsus DIAgNostIc-DrIVEN strAtEgIEs for ImmuNocomPromIsED PAtIENts WIth susPEctED AsPErgIllus INVAsIVE fuNgAl INfEctIoNs IN chINA Qin L.1, Chen Y.2, Lesher B.1, Liu Q.3, Charbonneau C.4, Earnshaw S.R.5, McDade C.5, Mao N.6, Gao X.1 1Pharmerit International, Bethesda, MD, USA, 2Pfizer Investment Co. Ltd., Beijing, China, 3Southern Medical UniversityNanfang Hospital, Guangzhou, China, 4Pfizer Inc, Paris, France, 5RTI Health Solutions, Research Triangle Park, NC, USA, 6China Pharmaceutical University, Nanjing, China OBJECTIVES: To examine the clinical and economic impact of diagnostic-driven (DD) versus empiric treatment strategies in neutropenic patients with suspected Aspergillus invasive fungal infections (IFIs) in Beijing, Chengdu, and Guangzhou, China. METHODS: A decision-analytic model was used to estimate total costs and survival associated with a DD and empiric treatment strategy for managing suspected IFIs in adult patients with neutropenia due to hematological malignancy or autologous/allogeneic stem cell transplant. In the DD strategy, IFI was identified via serum galactomannan (GM) enzyme-linked immunosorbent assay (ELISA) so that early initiation of targeted treatment could be administered. IFI incidence (10.9%), portion of actual IFIs diagnosed via empiric treatment (30%), overall mortality (10.7%), and IFI-related mortality (28.6%) were obtained from the literature. Survival rates were generated based on the proportion of patients with identified and appropriately treated IFIs. Empiric and DD treatment patterns and resource use were based on clinical opinion (3-5 clinicians from top hospitals per city). Medical costs (in 2014 Chinese Yuan [¥]) included antifungal drugs, treatment-related adverse events, and other medical resource costs. Cityspecific costing sources were used wherever possible. RESULTS: Medical costs were lower for the DD versus the empiric strategy in Beijing (¥4,118 vs ¥5,245), Chengdu, (¥5,463 vs ¥6,389), and Guangzhou (¥9,762 vs ¥10,351). Fewer patients received antifungal treatment using the DD strategy (6.7% versus 11.4%), and survival rates were similar. One-way sensitivity analysis showed results were most sensitive to changes in GM test sensitivity followed by IFI incidence. Probabilistic sensitivity analysis showed that treating via a DD strategy was dominant 99% of the time. CONCLUSIONS: These results suggest that in China, a DD strategy to identify IFIs in immunocompromised patients with persistent fever in order to better target antifungal treatment compared to an empiric antifungal treatment strategy may be cost-saving, while maintaining a similar overall survival rate.

Consensus guidelines for the use of empiric and diagnostic-driven antifungal treatment strategies in haematological malignancy, 2014.

Invasive fungal disease (IFD) causes significant morbidity and mortality in patients undergoing allogeneic haemopoietic stem cell transplantation or chemotherapy for haematological malignancy. Much of these adverse outcomes are due to the limited ability of traditional diagnostic tests (i.e. culture and histology) to make an early and accurate diagnosis. As persistent or recurrent fevers of unknown origin (PFUO) in neutropenic patients despite broad-spectrum antibiotics have been associated with the development of IFD, most centres have traditionally administered empiric antifungal therapy (EAFT) to patients with PFUO. However, use of an EAFT strategy has not been shown to have an overall survival benefit and is associated with excessive antifungal therapy use. As a result, the focus has shifted to developing more sensitive and specific diagnostic tests for early and more targeted antifungal treatment. These tests, including the galactomannan enzyme-linked immunosorbent assay and Aspergillus polymerase chain reaction (PCR), have enabled the development of diagnostic-driven antifungal treatment (DDAT) strategies, which have been shown to be safe and feasible, reducing antifungal usage. In addition, the development of effective antifungal prophylactic strategies has changed the landscape in terms of the incidence and types of IFD that clinicians have encountered. In this review, we examine the current role of EAFT and provide up-to-date data on the newer diagnostic tests and algorithms available for use in EAFT and DDAT strategies, within the context of patient risk and type of antifungal prophylaxis used.

Retrospective Comparison of Nucleic Acid Sequence–Based Amplification, Real-Time PCR, and Galactomannan Test for Diagnosis of Invasive Aspergillosis

Invasive aspergillosis is a life-threatening infection in immunocompromised patients, and treating these infections at an early stage is often crucial for a favorable outcome. Early diagnosis, however, remains challenging. We performed a retrospective comparison of three methods: real-time quantitative PCR (qPCR), nucleic acid sequence-based amplification (NASBA), and galactomannan enzyme-linked immunosorbent assay (GM-ELISA); these detect circulating Aspergillus DNA, RNA, and galactomannan, respectively. Blood samples from 80 patients at high risk for invasive aspergillosis were tested by each assay. The sensitivity of NASBA, qPCR, and GM-ELISA was 76.47% (95% CI, 58.4-88.6%), 67.65% (95% CI, 49.4-82.0%), and 52.94% (95% CI, 35.4-69.8%), respectively, and the specificity was 80.43% (95% CI, 65.6-90.1%), 89.13% (95% CI, 75.6-95.9%), and 80.43% (95% CI, 65.6-90.1%), respectively. We also evaluated the efficiency of the three tests in various combinations. Perfect specificity (100%; 95% CI, 90.4-100%) and perfect positive predictive value (100%; 95% CI, 77.1-100%) were achieved by combining NASBA and qPCR testing in series. Testing with both NASBA and qPCR in parallel was the most sensitive and had the highest Youden index. Our data support the great potential of NASBA and qPCR, singly or in combination, for diagnosis of invasive aspergillosis in high-risk populations.

Galactomannan-Based and PCR-Based Assays in Bronchoalveolar Lavage to Diagnose Invasive Aspergillosis: Current Status and Future Prospects

Invasive pulmonary aspergillosis (IPA) is a life-threatening complication in patients receiving chemotherapy or undergoing allogeneic haematopoietic stem cell transplantation for acute leukemia. The existing tools to diagnose IPA lack specificity or sensitivity, or both; the search for improved diagnostic tools for IPA has focused on novel serologic and molecular methods. Aspergillus Galactomannan enzyme-linked immunosorbent assay (GM) analyses showed sensitivity rates in serum samples ranging in a wide span; testing GM in bronchoalveolar lavage (BAL) originated from the primary site of the infection seems to be more sensitive in patients with IPA. Other novel diagnostic markers to detect fungal DNA directly in clinical samples, rapidly, early, sensitively and specifically, are provided by polymerase chain reaction (PCR) based assays; higher sensitivity and specificity rates have been observed for BAL samples in IPA, even under antifungal treatment. The clinical place value of a diagnostic approach combining PCR and GM in BAL is unclear.

The Effect Analysis of Different Experimental Methods for the Diagnosis of Invasive Pulmonary Aspergillosis in a Rat Model

Background: Consensus on the most reliable assays to detect invasive aspergillosis from minimally or noninvasive samples has not been reached. In this study, we compared the efficacy of an enzyme-linked immunosorbent assay (ELISA) for galactomannan (GM) detection and quantitative real-time PCR assay (qRT-PCR) for the diagnosis of invasive pulmonary aspergillosis in a rat model. Methods: Neutropenic, male Sprague-Dawley rats (specific pathogen free; 8 weeks old; weight, 200 ± 20 g) were immunosuppressed with cyclophosphamide and infected with Aspergillus fumigatus intratracheally. Tissue and whole blood samples were harvested on days 1, 3, 5, and 7 post-infection and examined with GM ELISA and qRT-PCR. Results: On day 7, A. fumigatus DNA was amplified from 14 of 48 whole blood samples from immunosuppressed infected rats: day 1 (0/12), day 3 (0/12), day 5 (6/12), day 7 (8/12) post infection. The sensitivity and specificity of the qRT-PCR assay were 29.2% and 100%, respectively. Receiver operating characteristic curve (ROC) analysis indicated a Ct cut-off value of 15.35, and the area under the curve (AUC) was 0.627. The GM assay detected antigen in sera obtained on day 1 (5/12), day 3 (9/12), day 5 (12/12), and day 7 (12/12) post-infection, and thus had a sensitivity of 79.2% and a specificity of 100%. The ROC of the GM assay indicated that the optimal cut-off value was 1.40 (specificity, 100%; AUC, 0.919). Conclusions: The GM assay was more sensitive than qRT-PCR assay in diagnosing invasive pulmonary aspergillosis in rats.

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).

Pathogen-Specific DNA Enrichment Does Not Increase Sensitivity of PCR for Diagnosis of Invasive Aspergillosis in Neutropenic Patients

PCR assays designed for the diagnosis of invasive aspergillosis (IA) in high-risk patients have to detect minute amounts of target DNA to reach sufficient analytical sensitivity to be of clinical use. This prospective study assessed the use of a novel strategy for selective pathogen DNA enrichment for enhancing the performance of diagnostic PCR in a direct comparison with a highly sensitive in-house quantitative PCR (qPCR) assay and the galactomannan enzyme-linked immunosorbent assay (ELISA). Surprisingly, and in contrast to experience with other patient groups, the novel protocol for selective pathogen DNA enrichment did not enhance but instead significantly impaired sensitivity. This could be explained by the small amounts of host DNA in the specimens, which were derived mostly from severely neutropenic patients. In the qPCR assay, positive samples required an average of 43.5 amplification cycles (range, 39.2 to 50) for detection in the in-house PCR. Repetitive testing of selected samples showed test positivity to be variable, most likely due to the small amounts of target DNA. Despite this, the in-house protocol proved helpful in the diagnosis of IA, detecting 2 out of 3 patients with probable IA and 10 out of 19 patients with possible IA. Our results underline the necessity for diagnostic PCR protocols that help diagnose IA to be highly sensitive and show that selective pathogen DNA enrichment using affinity purification may not be useful in severely neutropenic patients.

Opportunistic Fungi: A View to the Future

Opportunistic fungi are a constantly evolving group of pathogens that plague a growing group of vulnerable patients. These include hospitalized patients, especially those in the intensive care unit; stem cell and solid organ transplant recipients; patients treated with immunosuppressant medications; those with advanced human immunodeficiency virus or other acquired immunodeficiency conditions; and patients with organ failure syndromes. Rapid diagnosis of invasive fungal infection is essential to optimize outcomes. Several newer nonculture-based diagnostics, including the Aspergillus galactomannan enzyme-linked immunosorbent assay, the β-d-glucan assay and the multiplex polymerase chain reaction-based assays, may emerge as important tools facilitating early intervention with effective antifungal therapy. Newer azoles, including posaconazole, isavuconazole and ravuconazole, will potentially provide more effective therapeutic options in the future, diminishing the role for amphotericin B.

Contribution of the (1→3)-β- d -Glucan Assay for Diagnosis of Invasive Fungal Infections

Diagnosis of invasive fungal infection (IFI) remains a challenge. A retrospective study was performed on 279 patients at three French university hospitals to evaluate the performance of the (1-->3)-beta-D-glucan assay (BG assay; Fungitell; Associates of Cape Cod, Inc.) for the diagnosis of IFI. The results of one serum per subject were analyzed for 117 patients who had probable or proven IFI according to the European Organization for Research and Treatment of Cancer criteria (70 invasive pulmonary aspergilloses [IPA], 27 fungal bloodstream infections, and 20 Pneumocystis jiroveci pneumonias), 40 blood donors, and 122 patients who were hospitalized in hematology wards or intensive care units and were at risk for IFI but in whom IFI had not been diagnosed. For the overall IFI diagnosis, the BG assay had 77.8% sensitivity and specificities of 92.5 and 70.5% for blood donors and patients at risk, respectively. The assay was positive in 48 patients with IPA (68%), in 23 with bloodstream infections (85.2%), and in all who had P. jiroveci pneumonias (100%), and the false-positive rate varied depending on the controls used. It allowed a higher rate of detection among IPA patients compared to the galactomannan enzyme-linked immunosorbent assay (ELISA) (48 versus 39 patients, respectively) and among candidemia patients compared to the mannan ELISA (20 versus 11 patients, respectively). This assay therefore appears to be useful in the diagnosis of IFI, particularly for serum analysis of pneumocystosis pneumonia patients, but further studies are needed to evaluate false-positive rates and its future role in IFI diagnosis.

A comparison of galactomannan-ELISA and a newly developed galactomannan-LATEX test in the serologic diagnosis of invasive aspergillosis in patients with hematologic malignancies

We compared the sensitivity and specificity of galactomannan enzyme-linked immunosorbent assay (GM-ELISA) with that of a newly developed version of the commercially available latex agglutination test (GM-LATEX) in our patient population. Serum samples were collected from 144 healthy adult donors (controls); another 17 consecutive hematologic malignancy (HM) patients with probable or proven invasive aspergillosis (IA) were tested. Clinical, microbiological, and pathological data were obtained. The sensitivity of the GM-LATEX test was 53% per patient and 66% per sample and that of the GM-ELISA test was 41% per patient and 21% per sample. Both tests demonstrated a specificity of 99%. The GM-LATEX test demonstrated a superior sensitivity in terms of detecting galactomannan and thus may be useful in the diagnosis of IA in patients with HM.

Galactomannan Antigen Enzyme-Linked Immunosorbent Assay for Diagnosis of Invasive Aspergillosis after Hematopoietic Stem Cell Transplantation

Invasive aspergillosis is difficult to diagnose in patients undergoing hematopoietic stem cell transplantation (HSCT). In 2003, a serum enzyme-linked immunosorbent assay (ELISA) test for the detection of galactomannan (a glycoprotein found on the Aspergillus cell wall) became available in the United States. In 2004, patients undergoing HSCT were screened biweekly with the galactomannan ELISA at our institution. We performed a retrospective chart review of 121 SCT patients who underwent galactomannan testing. Thirteen of the patients (10.7%) had at least 1 positive galactomannan ELISA, and 4 had multiple positive tests. When calculated in reference to a proved or probable diagnosis of aspergillosis, the galactomannan ELISA had a sensitivity of 0.50 and a specificity of 0.94. The positive predictive value was 0.46, and the negative predictive value was 0.94. Galactomannan ELISA had fewer false-positive and false-negative results in pediatric patients than in adult patients. In 4 of the 12 cases of invasive aspergillosis, the galactomannan ELISA was positive before other microbiologic evidence of aspergillosis was available. In these cases, a positive ELISA predated culture and cytologic evidence of invasive aspergillosis by a mean of 5 days (range, 1-8 days). Our findings indicate that a biweekly serum galactomannan ELISA is a highly specific diagnostic tool for detecting invasive aspergillosis in patients undergoing HSCT. When used regularly, the ELISA may allow for earlier diagnosis of invasive aspergillosis in some patients. The test is troubled by a low sensitivity and high frequency of false-negative tests.