Diagnostic Values and Limitations of (1,3)-β-D-Glucans and Galactomannan Assays for Invasive Fungal Infection in Patients Admitted to Pediatric Intensive Care Unit

Serial (1-3)-beta-D-Glucan (BDG) monitoring shows high variability among premature neonates

This study aimed to characterize the baseline values and dynamics of serum (1,3)-Beta-D-Glucan (BDG) in neonates at high risk of neonatal invasive candidiasis (NIC); as well as to determine the effect of various clinical variables on these levels. Single center prospective cohort study was performed including 20 high-risk neonates (gestational age < 29 weeks and/or birth weight ≤ 1000 gr). Samples for BDG (Fungitell® assay) were obtained twice weekly during 6 weeks. Nineteen neonates were enrolled with a median gestational age of 25 weeks (IQR 24-27), median birth weight of 730 gr (IQR 650-810). None of the neonates was diagnosed with NIC. 190 serum samples were included. The median BDG value was 59 pg/ml (IQR 30-148), mean was 119 pg/ml (SD ± 154). A total of 42.1% (80/190) samples showed values ≥80 pg/ml, with all the neonates presenting at least one test above this cut-off. Neonatal age did not show an association with BDG levels. Exposure to steroids and the use of a heel prick as sampling method were associated with statistically significant higher BDG levels. The BDG levels showed high variability and in a significant proportion of samples values were above the threshold for positivity (e.g., ≥80 pg/ml) in the absence of NIC. The exposure to postnatal steroids and the heel prick as the method of blood sampling were associated with higher BDG levels.

LAY SUMMARY

Neonatal invasive candidiasis (NIC) presents high morbi-mortality. The diagnosis of NIC is often challenging. Blood cultures have limitations and better diagnostic tools are needed. Beta-D-glucan is a diagnostic marker which could be potentially used, although still more clinical data are required.

Comparative accuracy of 1,3 beta-D glucan and galactomannan for diagnosis of invasive fungal infections in pediatric patients: a systematic review with meta-analysis

Invasive fungal infections (IFI) cause considerable morbidity and mortality in pediatric patients. Serum biomarkers such as 1,3-beta-D glucan (BDG) and galactomannan (GM) have been evaluated for the IFI diagnosis. However, most evidence regarding their utility is derived from studies in adult oncology patients. This systematic review aimed to compare the diagnostic accuracy of BDG and GM individually or in combination for diagnosing IFI in pediatric patients. PubMed, CINAHL, Embase, and Cochrane Library were searched until March 2019 for diagnostic studies evaluating both serum GM and BDG for diagnosing pediatric IFI. The pooled diagnostic odds ratio (DOR), specificity and sensitivity were computed. Receiver operating characteristics (ROC) curve and area under the curve (AUC) were used for summarizing overall assay performance. Six studies were included in the meta-analysis. The summary estimates of sensitivity, specificity, pooled DOR, AUC of the GM assay for proven or probable IFI were 0.74, 0.76, 13.25, and 0.845. The summary estimates of sensitivity, specificity, pooled DOR, AUC of the BDG assay were 0.70, 0.69, 4.3, and 0.722. The combined predictive ability of both tests was reported in two studies (sensitivity: 0.67, specificity: 0.877). Four studies were performed in hematology-oncology patients, while two were retrospective studies from pediatric intensive care units (ICUs). In the subgroup of hematology-oncology patients, DOR of BDG remained similar at 4.25 but increased to 40.28 for GM. We conclude that GM and BDG have a modest performance for identifying IFI in pediatric patients. GM has a better accuracy over BDG. Combining both improves the specificity at the cost of sensitivity.

Challenges with Utilizing the 1,3-Beta-d-Glucan and Galactomannan Assays To Diagnose Invasive Mold Infections in Immunocompromised Children

Establishing the diagnosis of invasive mold infections (IMI) in immunocompromised children is challenging due to nonspecific clinical presentations and the limited sensitivity of traditional culture-based methods. Rapid non-culture-based diagnostics such as the 1,3-beta-d-glucan and galactomannan assays have emerged as promising adjuncts to conventional diagnostic tests in adults. Available data suggest that 1,3-beta-d-glucan has limited accuracy in the pediatric population and is not recommended to be used for the diagnosis of IMI in children. On the other hand, the diagnostic performance of the serum and bronchoalveolar lavage galactomannan in immunocompromised children is comparable to results observed in adults and can be used as a screening tool in children at high risk of developing invasive aspergillosis (IA) who are not receiving mold-active antifungal prophylaxis and as a diagnostic tool in symptomatic children suspected of having IA. Herein, we summarize the available evidence for the use of these rapid non-culture-based diagnostics in immunocompromised children. We also summarize potential causes of false positivity for the 1,3-beta-d-glucan and galactomannan assays.

Iron Assimilation during Emerging Infections Caused by Opportunistic Fungi with emphasis on Mucorales and the Development of Antifungal Resistance

Iron is a key transition metal required by most microorganisms and is prominently utilised in the transfer of electrons during metabolic reactions. The acquisition of iron is essential and becomes a crucial pathogenic event for opportunistic fungi. Iron is not readily available in the natural environment as it exists in its insoluble ferric form, i.e., in oxides and hydroxides. During infection, the host iron is bound to proteins such as transferrin, ferritin, and haemoglobin. As such, access to iron is one of the major hurdles that fungal pathogens must overcome in an immunocompromised host. Thus, these opportunistic fungi utilise three major iron acquisition systems to overcome this limiting factor for growth and proliferation. To date, numerous iron acquisition pathways have been fully characterised, with key components of these systems having major roles in virulence. Most recently, proteins involved in these pathways have been linked to the development of antifungal resistance. Here, we provide a detailed review of our current knowledge of iron acquisition in opportunistic fungi, and the role iron may have on the development of resistance to antifungals with emphasis on species of the fungal basal lineage order Mucorales, the causative agents of mucormycosis.

(1→3)-β-D-glucan testing for the detection of invasive fungal infections in immunocompromised or critically ill people

BACKGROUND

Invasive fungal infections (IFIs) are life-threatening opportunistic infections that occur in immunocompromised or critically ill people. Early detection and treatment of IFIs is essential to reduce morbidity and mortality in these populations. (1→3)-β-D-glucan (BDG) is a component of the fungal cell wall that can be detected in the serum of infected individuals. The serum BDG test is a way to quickly detect these infections and initiate treatment before they become life-threatening. Five different versions of the BDG test are commercially available: Fungitell, Glucatell, Wako, Fungitec-G, and Dynamiker Fungus.

OBJECTIVES

To compare the diagnostic accuracy of commercially available tests for serum BDG to detect selected invasive fungal infections (IFIs) among immunocompromised or critically ill people.

SEARCH METHODS

We searched MEDLINE (via Ovid) and Embase (via Ovid) up to 26 June 2019. We used SCOPUS to perform a forward and backward citation search of relevant articles. We placed no restriction on language or study design.

SELECTION CRITERIA

We included all references published on or after 1995, which is when the first commercial BDG assays became available. We considered published, peer-reviewed studies on the diagnostic test accuracy of BDG for diagnosis of fungal infections in immunocompromised people or people in intensive care that used the European Organization for Research and Treatment of Cancer (EORTC) criteria or equivalent as a reference standard. We considered all study designs (case-control, prospective consecutive cohort, and retrospective cohort studies). We excluded case studies and studies with fewer than ten participants. We also excluded animal and laboratory studies. We excluded meeting abstracts because they provided insufficient information.

DATA COLLECTION AND ANALYSIS

We followed the standard procedures outlined in the Cochrane Handbook for Diagnostic Test Accuracy Reviews. Two review authors independently screened studies, extracted data, and performed a quality assessment for each study. For each study, we created a 2 × 2 matrix and calculated sensitivity and specificity, as well as a 95% confidence interval (CI). We evaluated the quality of included studies using the Quality Assessment of Studies of Diagnostic Accuracy-Revised (QUADAS-2). We were unable to perform a meta-analysis due to considerable variation between studies, with the exception of Candida, so we have provided descriptive statistics such as receiver operating characteristics (ROCs) and forest plots by test brand to show variation in study results.

MAIN RESULTS

We included in the review 49 studies with a total of 6244 participants. About half of these studies (24/49; 49%) were conducted with people who had cancer or hematologic malignancies. Most studies (36/49; 73%) focused on the Fungitell BDG test. This was followed by Glucatell (5 studies; 10%), Wako (3 studies; 6%), Fungitec-G (3 studies; 6%), and Dynamiker (2 studies; 4%). About three-quarters of studies (79%) utilized either a prospective or a retrospective consecutive study design; the remainder used a case-control design. Based on the manufacturer's recommended cut-off levels for the Fungitell test, sensitivity ranged from 27% to 100%, and specificity from 0% to 100%. For the Glucatell assay, sensitivity ranged from 50% to 92%, and specificity ranged from 41% to 94%. Limited studies have used the Dynamiker, Wako, and Fungitec-G assays, but individual sensitivities and specificities ranged from 50% to 88%, and from 60% to 100%, respectively. Results show considerable differences between studies, even by manufacturer, which prevented a formal meta-analysis. Most studies (32/49; 65%) had no reported high risk of bias in any of the QUADAS-2 domains. The QUADAS-2 domains that had higher risk of bias included participant selection and flow and timing.

AUTHORS' CONCLUSIONS

We noted considerable heterogeneity between studies, and these differences precluded a formal meta-analysis. Because of wide variation in the results, it is not possible to estimate the diagnostic accuracy of the BDG test in specific settings. Future studies estimating the accuracy of BDG tests should be linked to the way the test is used in clinical practice and should clearly describe the sampling protocol and the relationship of time of testing to time of diagnosis.

Diagnosis of invasive fungal disease in children: a narrative review

Introduction: Invasive fungal diseases (IFD) represent important causes of morbidity and mortality in pediatrics. Early diagnosis and treatment of IFD is associated with better outcome and this entails the need to use fast and highly sensitive and specific methods that can support clinicians in the management of IFD.Areas covered: A narrative review was performed on conventional diagnostic methods such as culture, microscopy and histopathology are still gold standard but are burdened by a lack of sensitivity and specificity; on the other hand, imaging and noninvasive antigen-based such as beta-D-glucan, galactomannan and molecular biomarkers are the most convenient nonculture methods for diagnosis and monitoring effects of therapy. Aim of the present review is to summarize what is available in these fields at end of the second decade of the third millennium and look for future perspectives.Expert opinion: Promising and useful diagnostic methods have been applied in infectious disease diagnosis in clinical practice or in designing platforms. Unfortunately, most of them are not standardized or validated in pediatric population. However, clinicians should be aware of all innovative diagnostic tools to use in combination with conventional diagnostic methods for a better management of pathology and patient.

Role of serum (1,3)-β-d-glucan assay in early diagnosis of invasive fungal infections in a neonatal intensive care unit

OBJECTIVES

To study the microbiological pattern of late onset neonatal sepsis cultures and to assess the diagnostic performance of serum (1,3)-β-d-glucan level for early diagnosis of invasive fungemia in high-risk infants admitted to a neonatal intensive care unit.

METHODS

A prospective multicenter clinical trial conducted on infants at high risk for invasive fungal infections, with suspected late onset sepsis, admitted to a neonatal intensive care unit at Mansoura University Children's Hospital and Mansoura General Hospital between March 2014 and February 2016.

RESULTS

A total of 77 newborn infants with high risk of invasive fungal infection were classified based on blood culture into three groups: no fungemia (41 neonates with proven bacterial sepsis), suspected fungemia (25 neonates with negative blood culture), and definite fungemia group (11 neonates with culture-proven Candida). The growing organisms were Klebsiella spp. (14/54); Escherichia coli (12/54); Staphylococcus spp. (12/54; coagulase-negative Staphylococcus [9/54]; Staphylococcus aureus [3/54]); Pseudomonas aerouginosa (3/54); and Proteus spp. (2/54). Moreover, 11/54 presented Candida. Serum (1,3)-β-d-glucan concentration was significantly lower in the no fungemia group when compared with the definite fungemia group. The best cut-off value of (1,3)-β-d-glucan was 99pg/mL with sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of 63.6%, 95.1%, 77.8%, 90.7%, and 88.5%, respectively.

CONCLUSION

(1,3)-β-d-glucan assay has a limited sensitivity with excellent specificity and negative predictive value, which allow its use as an aid in exclusion of invasive neonatal fungal infection. Accurate diagnosis and therapeutic decisions should be based on combining (1,3)-β-d-glucan assay with other clinical, radiological, and microbiological findings.

Invasive fungal infections among critically ill children: Epidemiology, risk factors and outcomes

Critically ill children are at high risk of developing invasive fungal infection in a paediatric intensive care unit. This is due to the vulnerability of these children and invasive nature of the care provided.

Role of Molecular Biomarkers in the Diagnosis of Invasive Fungal Diseases in Children

Invasive fungal diseases are important clinical problems that are often complicated by severe illness and therefore the inability to use invasive measures to definitively diagnose the disease. Tests for a range of fungal biomarkers that do not require an invasive sample-collection procedure have been incorporated into adult clinical practice, but pediatric data and pediatric-specific recommendations for some of these diagnostic tools are lacking. In this review, we summarize the published literature and contemporary strategies for using the biomarkers galactomannan, (1→3)-β-d-glucan, Candida mannan antigen and anti-mannan antibody, and fungal polymerase chain reaction for diagnosing invasive fungal disease in children. Data on biomarker use in neonates and children with cancer, history of hematopoietic stem cell transplant, or primary immunodeficiency are included. Fungal biomarker tests performed on blood, other body fluids, or tissue specimens represent promising adjuncts to the diagnostic armamentarium in populations with a high prevalence of invasive fungal disease, but substantial gaps exist in the correct use and interpretation of these diagnostic tools in pediatric patients.