Efficacy of the new β-D-glucan measurement kit for diagnosing invasive fungal infections, as compared with that of four conventional kits

Diagnostic test accuracy of the Fungitell serum (1→3)-β-D-glucan assay for the diagnosis of Pneumocystis jirovecii pneumonia: a systematic review and meta-analysis

BACKGROUND

The diagnosis of Pneumocystis jirovecii pneumonia (PCP) can be challenging because of diagnostic tests that are imperfect and/or invasive. The Fungitell serum (1 → 3)-β-D-glucan (BDG) assay is a noninvasive blood test studied for PCP; however, the manufacturer-recommended cut-off of 80 pg/mL is not well validated for this disease.

OBJECTIVES

We conducted a systematic review and meta-analysis to determine the diagnostic test accuracy of the Fungitell BDG assay for the diagnosis of PCP.

METHODS

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DATA SOURCES

A search strategy of MEDLINE and Embase from a previous meta-analysis on BDG was updated to 31 January 2024.

STUDY ELIGIBILITY CRITERIA

Observational studies.

PARTICIPANTS

Patients with risk factors for PCP. TEST: Fungitell BDG assay.

REFERENCE STANDARD

One or more of lung biopsy, bronchoalveolar lavage, induced sputum, or nasopharyngeal swab specimens tested for PCP by histopathology, microscopy using immunofluorescence or staining, or PCR.

ASSESSMENT OF RISK OF BIAS

The Quality Assessment of Diagnostic Accuracy Studies-2 tool.

METHODS OF DATA SYNTHESIS

Diagnostic test accuracy data of the Fungitell serum BDG assay across all reported cut-offs were pooled by meta-analysis. We then evaluated a categorical approach using <80 pg/mL as a rule-out threshold and ≥400 pg/mL as a rule-in threshold.

RESULTS

A total of 26 articles were included comprising 5111 patients and 1150 PCP cases. At the conventional cut-off of 80 pg/mL, the overall pooled sensitivity and specificity were 83.5% (95% 95% CI, 72.8-90.6) and 75.5% (95% CI, 66.0-83.0), respectively. At a pretest probability of <20% and a BDG <80 pg/mL, the post-test probability would be <5% (negative predictive value > 95%). At 400 pg/mL, sensitivity was reduced to 63.5% (95% CI, 45.8-78.1) with specificity increased to 93.6% (95% CI, 88.6-96.5). At a pretest probability of 47.5%, a BDG >400 pg/mL would have a post-test probability of >90%.

DISCUSSION

A categorical approach using <80 pg/mL to rule-out and >400 pg/mL to rule-in PCP may allow for a more nuanced interpretation based on pretest probability. More accurate estimates of pretest probability and further external validation are required.

Progress on nonculture based diagnostic tests for invasive mould infection

PURPOSE OF REVIEW

This review describes the current status of diagnosing invasive mould disease and Pneumocystis pneumonia using nonconventional diagnostics methods.

RECENT FINDINGS

There has been significant development in the range of nonculture mycological tests. Lateral flow tests (LFTs) for diagnosing aspergillosis complement galactomannan ELISA testing, and LFTs for other fungal diseases are in development. Rapid and low through-put B-D-Glucan assays increase access to testing and there has been significant progress in the standardization/development of molecular tests. Despite this, no single perfect test exists and combining tests (e.g., antigen and molecular testing) is likely required for the optimal diagnosis of most fungal diseases.

SUMMARY

Based on established clinical performance few mycological tests can be used alone for optimal diagnosis of fungal disease (FD) and combining tests, including classical approaches is the preferred route for confirming and excluding disease. Next-generation sequencing will likely play an increasing role in how we diagnose disease, but optimization, standardization and validation of the entire molecular process is needed and we must consider how host biomarkers can stratify risk. Given the burden of FD in low- and medium-income countries, improved access to novel but more so existing diagnostic testing is critical along with simplification of testing processes.

Case report and literature review of refractory fungemia caused by Candidavulturna

Candida vulturna is a recently discovered and not widely documented ascomycetous yeast phylogenetically related to the outbreak-causing and multidrug-resistant Candida auris. A middle-aged Japanese man with no discernible immunodeficiency was admitted to hospital with ileal diverticulitis. Following laparoscopic right hemicolectomy against abscess formation on postoperative day (POD) 7, continuous fungemia occurred due to Candida haemulonii, identified using a conventional method by confirming the biochemical phenotype. Micafungin was initiated; however, the fungus was persistently isolated from blood cultures. Eventually, the antifungal agent was changed to a combination of liposomal amphotericin B (L-AMB) and caspofungin (CPFG), which cleared the infection, and no pathogens were detected in the blood cultures on POD 31. Contrast-enhanced computed tomography showed septic emboli in the lungs and spleen; however, no evidence of vasculitis was observed. Moreover, sequential echocardiography did not reveal any signs of infectious endocarditis. Finally, CPFG and L-AMB were administered to the patient for 7 and 9 weeks, respectively, during which the patient's symptoms did not relapse. The strain was later genetically identified as C. vulturna. This case report illustrates a clinical presentation of C. vulturna and provides the diagnostic approach and treatment methods for this pathogen.

UTILITY OF OCULAR β- d -GLUCAN TESTING IN PATIENTS WITH FUNGAL ENDOPHTHALMITIS

PURPOSE

To assess the diagnostic utility of (1→3)-β- d -glucan (BDG) in ocular fluid of patients with fungal endophthalmitis.

METHODS

This prospective pilot single-center study evaluated aqueous and vitreous humor BDG levels of suspected fungal endophthalmitis, bacterial endophthalmitis, and noninfectious controls with the standard Fungitell assay and the Fungitell STAT assay. β- d -Glucan levels were compared using generalized linear models followed by post hoc pairwise comparisons.

RESULTS

Seven fungal endophthalmitis, 6 bacterial endophthalmitis, and 17 noninfectious ocular samples were evaluated. Mean aqueous BDG concentrations were 204, 11.0, and 9.6 pg/mL for fungal endophthalmitis, bacterial endophthalmitis, and noninfectious controls, respectively ( P = 0.01, fungal vs. bacterial; P = 0.0005, fungal vs. noninfectious controls). Mean vitreous BDG concentrations were 165, 30.3, and 5.4 pg/mL, respectively ( P = 0.001 for fungal vs. bacterial; P < 0.0001 for fungal vs. noninfectious controls). Mean vitreous BDG index (Fungitell STAT) values were 1.7, 0.4, and 0.3, respectively ( P = 0.001, fungal vs. bacterial; P = 0.0004, fungal vs. noninfectious controls). The Pearson correlation between BDG levels and BDG index was high (correlation coefficient = 0.99, P < 0.001).

CONCLUSION

Significantly elevated ocular BDG levels were found in fungal endophthalmitis compared with bacterial endophthalmitis and noninfectious controls. Our study suggests a potential utility for BDG testing in the diagnosis of fungal endophthalmitis, and a larger study is warranted.

A scoring system based on novel biomarkers and clinical risk factors to predict invasive candidiasis in immunocompetent critically ill patients

Background

Delayed diagnosis further increases the mortality of invasive candidiasis (IC) in intensive care unit (ICU) patients. This study aimed to develop and validate a score based on novel serological biomarkers and clinical risk factors for predicting IC in immunocompetent ICU patients.

Methods

We retrospectively collected clinical data and novel serological markers on admission to ICU. Multivariate logistic regression was used to identify the risk factors associated with IC, which were adopted to establish a scoring system.

Results

Patients with IC had a higher C-reactive protein-to-albumin ratio (CAR) and neutrophil-to-lymphocyte ratio (NLR) and lower prognostic nutritional index than those without IC. The NLR, CAR, sepsis, total parenteral nutrition, 1,3-β-D-glucan (BDG)-positivity, and Sequential Organ Failure Assessment score were identified as independent risk factors for IC by multivariate logistic regression analysis and entered into the final scoring system. The area under receiver operating characteristic curve of the score were 0.883 and 0.892, respectively, in the development and validation cohort, higher than Candida score (0.883 vs.0.730, p &lt; 0.001).

Conclusion

We established a parsimonious score based on NLR, CAR, BDG-positivity, and clinical risk factors, which can accurately identify IC in ICU patients to give treatment on time and reduce mortality.

Comparison of Three β-Glucan Tests for the Diagnosis of Invasive Candidiasis in Intensive Care Units

The (1→3)-β-d-glucan (BDG) is a marker of invasive fungal infection that can be detected in serum by different commercial kits. In this study, we compared the performance of the Fungitell assay (FA), the Fungitell STAT assay (STAT), and the Wako β-glucan test (WA) for the diagnosis of invasive candidiasis (IC) in the intensive care unit (ICU). Patients for whom at least one BDG testing was required for a clinical suspicion of IC were retrospectively enrolled. A total of 85 serum samples from 56 patients were tested by the three BDG tests. The rate of IC was 23% (13/56) with a predominance of noncandidemic (intra-abdominal) IC. STAT and WA results exhibited overall good correlation with those obtained by FA (Spearman's coefficient R = 0.90 and R = 0.89, respectively). For the recommended cutoffs of positivity, sensitivity and specificity for IC diagnosis were 77%/51% (FA, 80 pg/mL), 69%/53% (STAT, ratio 1.2), and 54%/65% (WA, 7 pg/mL), respectively. Optimal performance was obtained at 50 pg/mL (FA), ratio 1.3 (STAT), and 3.3 pg/mL (WA) with sensitivity/specificity of 85%/51%, 69%/57%, and 77%/58%, respectively. Overall, the three BDG tests showed comparable but limited performance in this setting with positive and negative predictive values for an estimated IC prevalence of 20% that were in the range of 30 to 35% and 85 to 95%, respectively.

The Comparative Evaluation of the Fujifilm Wako β-Glucan Assay and Fungitell Assay for Diagnosing Invasive Fungal Disease

Serum 1,3-β-d-glucan(BDG) is a broad fungal biomarker for invasive fungal disease (IFD). More data is still required to support the Fujifilm Wako assay as a valuable alternative to the widely used Fungitell assay. We included archived serum samples from 157 individuals (97 cases; 33-IA, 64-IC, and 60 controls) for the comparative performance evaluation of the Fungitell assay and the Fujifilm Wako assay for IFD diagnosis. The BDG value was significantly higher in patients with IFD vs. controls (70.79 pg/mL vs. 3.03 pg/mL, p: 0.0002). An area under the curve (AUC) for the IFD, IC, and IA diagnosis was 0.895, 0.910, and 0.866, respectively, for the Fujifilm Wako assay. Based on the highest Youden’s index (0.667), a cutoff of 5 pg/mL was selected as the optimum for the Fujifilm Wako assay with good sensitivity (79.4%), specificity (88.3%) and agreement (84.7%, Cohen’s k:0.691) with the Fungitell assay. The mean run-time of the Fujifilm Wako assay was 70.12 min, and real-time observation allowed earlier time to result in Fujifilm Wako vs. Fungitell assay (37 vs. 120 min, p: < 0.0001). Thus, our findings support the diagnostic value of the Fujifilm Wako assay for the diagnosis of IFD. However, there is still a need to validate diagnostic protocols to optimize their use in multi-centre studies with different patient groups.

Beta-D-Glucan in Patients with Haematological Malignancies

(1-3)-beta-D-glucan (BDG) is an almost panfungal marker (absent in zygomycetes and most cryptococci), which can be successfully used in screening and diagnostic testing in patients with haematological malignancies if its advantages and limitations are known. The aim of this review is to report the data, particularly from the last 5 years, on the use of BDG in haematological population. Published data report mainly on the performance of the Fungitell™ assay, although several others are currently available, and they vary in method and cut-off of positivity. The sensitivity of BDG for invasive fungal disease (IFD) in haematology patients seems lower than in other populations, possibly because of the type of IFD (lower sensitivity was found in case of aspergillosis compared to candidiasis and pneumocystosis) or the use of prophylaxis. The specificity of the test can be improved by using two consecutive positive assays and avoiding testing in the case of the concomitant presence of factors associated with false positive results. BDG should be used in combination with clinical assessment and other diagnostic tests, both radiological and mycological, to provide maximum information. Good performance of BDG in cerebrospinal fluid (CSF) has been reported. BDG is a useful diagnostic method in haematology patients, particularly for pneumocystosis or initial diagnosis of invasive fungal infections.