Clinical Accuracy and Impact of Plasma Cell-Free DNA Fungal PCR Panel for Non-Invasive Diagnosis of Fungal Infection

Role of liposomal amphotericin B in intensive care unit: an expert opinion paper

INTRODUCTION

Invasive fungal infections (IFI) are frequent in patients admitted to the intensive care unit (ICU). The use of first-line antifungals like triazoles or echinocandins may be limited by the global spread of multi-drug resistance species, drug-drug interactions, low organ penetration, and some safety concerns in case of multi-organ failure. Liposomal amphotericin B (L-AmB) is a polyene drug with a broad activity against mold and yeast and an acceptable safety profile. To outline the role of L-AmB in the treatment of IFI in critically ill patients, a panel of experts was invited to draw up an expert opinion paper on the appropriate place in therapy of L-AmB in different clinical scenarios of patients admitted to ICU.

METHODS

A multidisciplinary group of 16 specialists in infectious disease, microbiology, pharmacology, and intensive care elaborated an expert opinion document through a multi-step approach: (1) the scientific panel defined the items and wrote the statements on the management of IFI in ICU, (2) a survey was submitted to an external panel to express agreement or disagreement on the statements, and (3) the panel reviewed the survey and implemented the final document.

RESULTS

The final document included 35 statements that focused on epidemiology and microbiological rationale of the use of systemic L-AmB in critically ill patients and its potential role in specific clinical scenarios in the ICU.

CONCLUSION

Systemic L-AmB may represent an appropriate therapeutic choice for IFI in ICU patients with different underlying conditions, especially when the use of first-line agents is undermined. This expert opinion paper may provide a useful guide for clinicians.

Sensitivity and Specificity of Plasma and Bronchoalveolar Lavage Fluid PCR for Diagnosing Pulmonary Mucormycosis in Subjects With Diabetes Mellitus

BACKGROUND

Mucorales polymerase chain reaction (PCR) is used to diagnose pulmonary mucormycosis (PM) among neutropenic individuals. However, data on the utility of PCR in patients with diabetes mellitus, another major risk factor for PM, are limited.

OBJECTIVE

The primary objective was to assess the diagnostic performance of a commercial real-time PCR assay (MucorGenius) in plasma and bronchoalveolar lavage fluid (BALF) for diagnosing PM (proven and probable cases only) in patients with suspected invasive mould disease (IMD). For the secondary objective, we evaluated the performance of the MucorGenius assay in all PM (proven, probable, and possible) cases.

METHODS

We prospectively enrolled patients with suspected IMD and assessed the performance of MucorGenius PCR (index test) in plasma and BALF samples. A multidisciplinary team assigned the final diagnosis of IMD (reference standard) based on microscopy, histopathology, cytology, and culture. We report the sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) with 95% confidence intervals (CI).

RESULTS

We enrolled 103 patients, of whom 43 (41.7%) were confirmed to have PM. Plasma PCR showed a sensitivity of 18.6% (95% CI: 8.4-33.4), specificity of 90.7% (95% CI:77.9-97.4), PPV of 66.7%, and NPV of 52.7%. Including possible PM/IMD cases improved the plasma PCR sensitivity to 30.0% (95% CI: 18.9-43.2) and retained specificity at 90.7%. BALF PCR had better sensitivity (47.4%) but poorer specificity (69.6%), with a PPV of 56.3% and NPV of 61.5%.

CONCLUSION

Plasma and BALF MucorGenius PCR have poor diagnostic performance for diagnosing PM among individuals with diabetes mellitus. Further multicenter studies are needed to validate these findings.

Invasive Candidiasis in the Intensive Care Unit: Where Are We Now?

Invasive fungal infections in the intensive care unit (ICU) are not uncommon and most cases are caused by Candida species, specifically Candida albicans. However, recently, there has been an increase in non-albicans Candida spp. (C. glabrata; C. parapsilosis) causing invasive fungal infections. This has led to an increasing awareness of this infection due to the increase in documented antifungal resistance in many of these Candida species. In addition, manifestations of invasive candidiasis are often non-specific, and the diagnosis remains extremely challenging. Unfortunately, delays in antifungal therapy continue to hamper the morbidity; length of stay; and the mortality of these infections. Although the echinocandins are the drugs of choice in these infections, antifungal resistance among the non-albicans species (C. glabrata; C. krusei; C. auris; C. parapsilosis) is being observed more frequently. This has led to an increase in morbidity and mortality, specifically in critically ill patients. Overall, the diagnosis and management of invasive candidiasis in the ICU remain challenging. It is imperative that the critical care physician keeps this infection at the forefront of their differential diagnosis in order to decrease the mortality rate of these individuals. In this review, we discuss the current epidemiologic trends, diagnosis, and management of invasive candidiasis in the intensive care unit setting.

The diagnosis of mucormycosis by PCR in patients at risk: a systematic review and meta-analysis

Background

This systematic review and meta-analysis aimed to examine the performance of polymerase chain reaction (PCR) assays for diagnosing mucormycosis.

Methods

A standardised search was conducted from conception to December 3rd 2024 using PubMed, Embase, Global Health, and Cochrane library. Original studies that used PCR-based methods on any human specimen to diagnose mucormycosis were analysed for eligibility. Using a bivariate meta-analysis, the diagnostic performance of PCR was examined against the European Organisation for Research and Treatment of Cancer-Mycoses Study Group Education and Research Consortium 2020 (EORTC-MSGERC) definitions of proven and probable invasive mould disease, which was modified to include all patients at risk of mucormycosis. The study protocol was registered on the PROSPERO database (CRD42023478667).

Findings

Of 4855 articles, a total of 30 met inclusion criteria, including 5920 PCR reactions on 5147 non-duplicate specimens from 819 cases of proven/probable mucormycosis and 4266 patients who did not meet the EORTC-MSGERC 2020 criteria. According to specimen type, sensitivity of PCR varied (p < 0.001) whereas specificity was similar (p = 0.662). Bronchoalveolar lavage fluid offered the highest sensitivity of 97.5% (95% CI 83.7-99.7%), specificity of 95.8% (95% CI 89.6-98.4%), positive likelihood ratio (LR+) of 23.5, and negative likelihood ratio (LR-) of 0.03. Tissue provided sensitivity of 86.4% (95% CI 78.9-91.5%), specificity of 90.6% (95% CI 78.1-96.3%), LR+ of 9.2, and LR- of 0.15. Blood provided reduced sensitivity of 81.6% (95% CI 70.1-89.4%), specificity of 95.5% (95% CI 87.4-98.5%), DOR of 95, LR+ of 18.3, and LR- of 0.19. Formalin-fixed paraffin-embedded specimens yielded the lowest sensitivity of 73.0% (95% CI 61.0-82.3%), highest specificity of 96.4% (CI 95% 87.5-99.0%), LR+ of 20.2, and LR- of 0.28. The covariates best explaining heterogeneity of the overall analysis were specimen type, study design (cohort versus case-control) and disease prevalence while patient population (COVID-19 versus other) and PCR (conventional versus quantitative) had less impact on heterogeneity.

Interpretation

This meta-analysis confirms the high performance of PCR for diagnosing mucormycosis and supports the instatement of PCR detection of free-DNA in blood, BALF and tissue into future updated definitions and diagnostic guidelines for mucormycosis.

Funding

None.

Recent Developments in Culture-Independent Fungal Diagnostics

Culture-independent diagnostics for fungi potentially offer increased sensitivity and more rapid results relative to culture. Recent developments include new platforms for fungal cell wall antigen detection, commercially available targeted nucleic acid amplification tests, and the use of sequencing-based technologies for the detection and identification of a broad range of fungal pathogens. Although these tests are not without limitations, many more commercially available platforms now exist, and efforts to increase the standardization of laboratory-developed tests are ongoing. Additionally, implementation studies are beginning to delineate the optimal use cases for molecular diagnostics across a range of fungal diseases and at-risk populations.

Interlaboratory assays from the fungal PCR Initiative and the Modimucor Study Group to improve qPCR detection of Mucorales DNA in serum: one more step toward standardization

The aim of this study was to identify parameters influencing DNA extraction and PCR amplification efficiencies in an attempt to standardize Mucorales qPCR. The Fungal PCR Initiative Mucorales Laboratory Working Group distributed two panels of simulated samples to 26 laboratories: Panel A (six sera spiked with Mucorales DNA and one negative control serum) and Panel B (six Mucorales DNA extracts). Panel A underwent DNA extraction in each laboratory according to the local procedure and were sent to a central laboratory for testing using three different qPCR techniques: one in-house qPCR assay and two commercial assays (MucorGenius and Fungiplex). Panel B DNA extracts were PCR amplified in each laboratory using local procedures: nine in-house qPCR assays and two commercial kits (MucorGenius and MycoGENIE). All data were compiled and anonymously analyzed at the central laboratory. For Panel A, a total of six different automated platforms and five manual extraction methods were used. Positive rates were 64%, 70%, and 89%, for the MucorGenius, Fungiplex, and the in-house qPCR assay, respectively. Using a large volume of serum for DNA extraction provided the highest analytical sensitivity (82.5% for 1 mL compared with 62.7% for smaller volumes, P < 0.01). For Panel B, five in-house qPCR assays and two commercial kits had >78% positivity. Using larger PCR input volumes (≥7 µL) was associated with the highest sensitivity at 95.5% compared to 58.3% when lower input volumes were used (P < 0.01). Using larger sample volumes for nucleic acid extraction and DNA template volumes for PCR amplification significantly improves the performance of Mucorales qPCR when testing serum.

IMPORTANCE

Mucormycosis is a life-threatening mold infection affecting immunosuppressed patients but also other patients with diabetes or trauma. Better survival is linked to shorter delays in diagnosis and treatment initiation. Detection of Mucorales-free DNA in serum or plasma using quantitative PCR allows a prompt diagnosis and earlier treatment. Several techniques and protocols of quantitative Mucorales PCR are used in Europe, and improving performance remains a common objective of laboratories participating in the fungal PCR Initiative Working Group. This study, which combined results from 26 laboratories in Europe, showed that the main parameters underpinning sensitivity are the preanalytical variables (volume of serum used for DNA extraction and DNA template volume), irrespective of the extraction platforms and qPCR assay/platform.

One Size Fits Small: The Narrow Utility for Plasma Metagenomics

Metagenomic sequencing of plasma has been advertised by Karius, Inc. as a way to diagnose a variety of infectious syndromes. Due to the lack of robust evidence of clinical utility, our laboratory began actively stewarding Karius testing. Microbiology Directors recommended cancelation of Karius orders when certain criteria were identified. We set out to review Karius test requests in a 52-month period of stewardship, during which we recommended cancellation on 21 of 57 orders (37%). Of Karius tests sent on samples with negative conventional testing, only 3 (7%) had positive results for Karius with plausible explanatory etiologies. Of these three cases, two were empirically covered for the positive finding without improvement and one case was never treated. Twelve (29%) had positive results that were noted by infectious diseases (ID) to reflect insignificant detections. Given the 4-fold higher detection of insignificant Karius results, we set out to systematically analyze the literature for the experience of insignificant detections at other centers. When we compared studies that included healthy controls or had clinical adjudication of positive Karius findings by ID physicians, we found a median of 17.5% of individual patients that had positive insignificant detections of potential pathogenic bacteria or fungi. The most frequently detected species were as likely to be clinically adjudicated to be insignificant as they were to be significant within the same studies. Overall, these findings highlight limited utility of Karius testing and a need for careful stewardship, not only to ensure it is sent on patients who may benefit, but also to ensure results of potential pathogens are interpreted cautiously.

Yield of clinical metagenomics: insights from real-world practice for tissue infections

BACKGROUND

While metagenomic next-generation sequencing (mNGS) has been acknowledged as a valuable diagnostic tool for infections, its clinical validity and impact on patient management when using fresh tissue samples remains uncertain.

METHODS

We conducted a retrospective cross-sectional study involving patients who underwent tissue mNGS at a tertiary hospital in China from February 2021 to February 2024, aiming to assess its ability to detect plausible pathogens and its clinical validity and impact.

FINDINGS

A total of 520 mNGS results from 508 patients were analysed, detecting plausible pathogens in 302 (58.1%) tests, including 260 single-pathogen and 42 (13.9%) multi-pathogen results. Rare pathogens, such as Balamuthia mandrillaris, Bartonella henselae, and Sporothrix globosa, were identified. Of the multi-pathogen results, 22 were with predominance of anaerobes. mNGS showed higher positivity in cases with high initial suspicion of infection than those used for ruling out infection (PR 1.961, 95% CI: 1.604-2.394) and in patients living with HIV (PR 1.312, 95% CI: 1.047-1.643) or solid organ transplant recipients (PR 1.346, 95% CI: 1.103-1.643) compared to immunocompetent individuals. Sensitivity and specificity for diagnosing confirmed/probable infections were 85.0% (95% CI: 76.7%-93.3%) and 93.7% (95% CI: 86.8%-100.0%), respectively. mNGS influenced clinical management in 258 (49.6%) cases by identifying new infections and in 112 (21.5%) by excluding infections. It prompted initiation (20.2%), modification (23.1%), or discontinuation (6.3%) of antimicrobial therapy.

INTERPRETATION

mNGS demonstrates high diagnostic accuracy for tissue infections. Its impact on clinical management highlights the need to integrate it into current diagnostic practices.

FUNDING

National Natural Science Foundation of China (No. 82472371), "Leading Geese" Research and Development Plan of Zhejiang Province (No. 2024C03218), and Pudong New Area Joint Project (PW2021D-09).

A fatal case of disseminated Cladophialophora bantiana infection in a renal transplant recipient

Dematiaceous molds often cause noninvasive disease but have the potential to cause disseminated infection, particularly in immunosuppressed hosts. Cladophialophora bantiana is the most neurotropic of dematiaceous molds and is associated with brain abscesses, but disseminated infection is quite rare. Here we present a case of disseminated C. bantiana in a 67-year-old renal transplant recipient with multifocal soft tissue, bone and presumed central nervous system involvement. C. bantiana infections have been associated with significant mortality and our patient had progression of his disease despite intensive dual antifungal therapy with close therapeutic drug monitoring. There was a delay in diagnosis and initiation of antifungal therapy as the multifocal disease was presumed to represent a malignant process. This case review highlights the importance of having a high index of suspicion for disseminated fungal infection in immunocompromised patients and the need for tissue biopsy to aid in the prompt and timely diagnosis and initiation of empiric antifungal therapy, with concomitant surgical management whenever possible to improve patient outcomes.

Application of Diagnostic Stewardship to Fungal Polymerase Chain Reaction: Low Yield of Follow-up Testing on Plasma and Bronchoalveolar Lavage After a Negative Result

BACKGROUND

Early diagnosis of invasive fungal disease is essential for optimizing management. Although the clinical utility of fungal polymerase chain reaction (PCR) testing on plasma and bronchoalveolar lavage (BAL) has been established, the role of follow-up testing remains unclear.

METHODS

This was a retrospective single-center study. The yield of follow-up PCR for Aspergillus species, Mucorales agents, Fusarium species, Scedosporium species, dimorphic fungi, Pneumocystis jirovecii, and Candida species on plasma and/or BAL was measured at intervals of 1, 2, 3, and 4 weeks following a negative result.

RESULTS

A total of 1389 follow-up tests on 406 plasma specimens from 264 patients and 983 BAL specimens from 431 patients were evaluated. Overall, the positivity rate at 1, 2, 3, and 4 weeks was 2.7% (4/148), 3.3% (4/123), 5.1% (4/78), and 3.5% (2/57), respectively, on plasma, and 0% (0/333), 0.3% (1/288), 0.4% (1/228), and 0.7% (1/134), respectively, on BAL. Conversions occurred with Aspergillus species, Mucorales agents, and Fusarium species PCR on plasma and Aspergillus species and P jirovecii PCR on BAL. All patients who converted were immunocompromised. Within 1 week of a prior negative test, 2 Aspergillus and 2 Mucorales PCRs were positive on plasma, and zero tests were positive on BAL. In week 1, only 1 Aspergillus species that was positive on day 7 was classified as probable fungal disease.

CONCLUSIONS

Fungal PCR follow-up testing on plasma and BAL within 4 weeks of a prior negative result was of low yield and rarely generated a positive result considered clinically significant in the first week.

Application of cell-free DNA fungal polymerase chain reaction for invasive fungal disease evaluation in pediatric oncology and stem cell transplant patients

BACKGROUND

Molecular diagnostics may enable early, noninvasive detection of invasive fungal disease (IFD) in immunocompromised patients. Cell-free deoxyribonucleic acid (cfDNA) fungal polymerase chain reaction (PCR) assays were recently incorporated into institutional prolonged febrile neutropenia pathways. We aimed to evaluate the performance of plasma cfDNA PCR panels (mold and Candida panels) in pediatric oncology and hematopoietic stem cell transplant (HSCT) patients with clinical concern for IFD.

METHODS

This single-center, observational study assessed plasma cfDNA fungal PCR performance for noninvasive IFD detection in hospitalized pediatric oncology and HSCT patients. The primary outcome was IFD diagnosis per published consensus definitions within 1 month. Positive and negative agreement between plasma cfDNA fungal PCR and consensus definitions were calculated. We also described test turnaround time and patient survival.

RESULTS

From October 2021 to 2022, 54 patients underwent 60 evaluations with 11 proven/probable IFD cases. Comparing plasma cfDNA fungal PCRs to consensus definitions for proven/probable IFD, there was 73% positive agreement and 96% negative agreement. Two proven/probable cases with negative PCRs were caused by organisms not included on either panel. Median time to cfDNA fungal PCR result was 35 hours (interquartile range: 19-69) in eight proven/probable cases detected by cfDNA fungal PCR. There were 17 deaths among 54 patients, and IFD contributed to 45% of deaths in patients with proven/probable IFD.

CONCLUSIONS

Plasma cfDNA fungal PCRs detected relevant molds or yeast in most cases classified as proven/probable IFD. However, this targeted approach missed some cases. More studies are required to determine optimal utilization of molecular diagnostics in pediatric patients.

Liquid Biopsy Based on Cell-Free DNA and RNA

This review delves into the rapidly evolving landscape of liquid biopsy technologies based on cell-free DNA (cfDNA) and cell-free RNA (cfRNA) and their increasingly prominent role in precision medicine. With the advent of high-throughput DNA sequencing, the use of cfDNA and cfRNA has revolutionized noninvasive clinical testing. Here, we explore the physical characteristics of cfDNA and cfRNA, present an overview of the essential engineering tools used by the field, and highlight clinical applications, including noninvasive prenatal testing, cancer testing, organ transplantation surveillance, and infectious disease testing. Finally, we discuss emerging technologies and the broadening scope of liquid biopsies to new areas of diagnostic medicine.

Diagnostic Value of Microbial Cell-free DNA Sequencing for Suspected Invasive Fungal Infections: A Retrospective Multicenter Cohort Study

Background

An early diagnosis and treatment of invasive fungal disease (IFD) is associated with improved outcome, but the moderate sensitivity of noninvasive diagnostic tests makes this challenging. Invasive diagnostic procedures such as bronchoalveolar lavage (BAL) have a higher yield but are not without risk. The detection and sequencing of microbial cell-free DNA (mcfDNA) may facilitate a noninvasive diagnosis.

Materials

In a prospective observational study, we collected plasma in the 120 hours preceding or following a BAL in patients with hematological malignancies suspected for a pulmonary IFD. The EORTC/MSGERC2020 criteria were used for IFD classification. Sequencing was performed by Karius (Redwood City, CA) using their Karius Test (KT) on plasma and a "research use only test" on BAL fluid if available. Cases with a probable/proven IFD were identified based on standard diagnostic tests on serum and BAL (microscopy, polymerase chain reaction, galactomannan, culture) and used to calculate the sensitivity, specificity, and additional diagnostic value of the KT.

Results

Of 106 patients enrolled, 39 (37%) had a proven/probable invasive aspergillosis, 7 (7%) a non-Aspergillus IFD, and 4 (4%) a mixed IFD. The KT detected fungal mcfDNA in 29 (28%) patients. Compared with usual diagnostic tests, the sensitivity and specificity were 44.0% (95% confidence interval [CI], 31.2-57.7) and 96.6% (95% CI, 88.5%-99.1%). Sensitivity of the KT was higher in non-Aspergillus IFD (Mucorales:2/3, Pneumocystis jirovecii: 3/5). On BAL, the sensitivity was 72.2% (95% CI, 62.1-96.3), and specificity 83.3% (95% CI, 49.1-87.5).

Conclusions

Sequencing of mcfDNA may facilitate a noninvasive diagnosis of IFD in particular non-Aspergillus IFD. However, on plasma and similar to currently available diagnostics, it cannot be used as a "rule-out" test.

Dynamics and prognostic value of plasma cell-free DNA PCR in patients with invasive aspergillosis and mucormycosis

Aspergillus species and Mucorales agents are the primary etiologies of invasive fungal disease (IFD). Biomarkers that predict outcomes are needed to improve care. Patients diagnosed with invasive aspergillosis and mucormycosis using plasma cell-free DNA (cfDNA) PCR were retested weekly for 4 weeks. The primary outcome included all-cause mortality at 6 weeks and 6 months based on baseline cycle threshold (CT) values and results of follow-up cfDNA PCR testing. Forty-five patients with Aspergillus and 30 with invasive Mucorales infection were retested weekly for a total of 197 tests. Using the European Organization for Research and Treatment of Cancer and the Mycoses Study Group Education and Research Consortium (EORTC/MSG) criteria, 30.7% (23/75), 25.3% (19/75), and 38.7% (29/75) had proven, probable, and possible IFD, respectively. In addition, 97.3% (73/75) were immunocompromised. Baseline CT increased significantly starting at week 1 for Mucorales and week 2 for Aspergillus. Aspergillosis and mucormycosis patients with higher baseline CT (CT >40 and >35, respectively) had a nonsignificantly higher survival rate at 6 weeks, compared with patients with lower baseline CT. Mucormycosis patients with higher baseline CT had a significantly higher survival rate at 6 months. Mucormycosis, but not aspergillosis patients, with repeat positive cfDNA PCR results had a nonsignificantly lower survival rate at 6 weeks and 6 months compared with patients who reverted to negative. Aspergillosis patients with baseline serum Aspergillus galactomannan index <0.5 and <1.0 had significantly higher survival rates at 6 weeks when compared with those with index ≥0.5 and ≥1.0, respectively. Baseline plasma cfDNA PCR CT can potentially be used to prognosticate survival in patients with invasive Aspergillus and Mucorales infections.

IMPORTANCE

We show that Aspergillus and Mucorales plasma cell-free DNA PCR can be used not only to noninvasively diagnose patients with invasive fungal disease but also to correlate the baseline cycle threshold with survival outcomes, thus potentially allowing the identification of patients at risk for poor outcomes, who may benefit from more targeted therapies.

Antifungal stewardship in practice: Insights from a prospective audit and feedback program

OBJECTIVE

To identify characteristics of antifungal prospective audit and feedback (PAF) and to compare rates of PAF recommendation and acceptance between antifungal and antibiotic agents.

DESIGN

Retrospective cohort study of antifungal and antibiotic audits by a children's hospital antimicrobial stewardship program (ASP) from November 1, 2020, to October 31, 2022.

METHODS

Antimicrobial audit data were retrieved from the ASP data warehouse. We characterized antifungal PAF using descriptive statistics. We then compared the overall rates of PAF recommendation and recommendation acceptance between antifungals and antibiotics. We also compared the differences in antifungal and antibiotic PAF recommendation and acceptance rates across various factors, including infectious problem, medical service, and recommendation type.

RESULTS

Of 10,402 antimicrobial audits identified during the study period, 8,599 (83%) were for antibiotics and 1,803 (17%) were for antifungals. The highest antifungal recommendation rates were for liposomal amphotericin B, antifungals used for sepsis or respiratory tract infection, and antifungals prescribed in the cardiovascular intensive care unit. The rate of PAF recommendation was higher for antibiotics than for antifungals (29% vs 21%; P < .001); however, the rates of recommendation acceptance were similar. Recommendations to discontinue or for medication monitoring were more common for antifungals.

CONCLUSIONS

Our analysis of antifungal PAF identified key opportunities to improve antifungal use, including the optimized use of specific agents and targeted use by certain medical services. Moreover, antifungal PAF, despite identifying fewer recommendations compared to antibiotic PAF, were associated with similarly high rates of acceptance, highlighting a promising opportunity for antifungal stewardship.

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.

Microbial cell-free DNA detection: Minimally invasive diagnosis of infectious diseases

BACKGROUND

Detection of infectious diseases, especially among immunocompromised and patients on prolonged anti-microbial treatment, remains challenging, limited by conventional techniques with low sensitivity and long-turnaround time. Molecular detection by polymerase chain reaction (PCR) also has limited utility as it requires a targeted approach with prior suspicion of the infecting organism. Advancements in sequencing methodologies, specifically next-generation sequencing (NGS), have presented a promising opportunity to identify pathogens in cases where conventional techniques may be inadequate. However, the direct application of these techniques for diagnosing invasive infections is still limited by the need for invasive sampling, highlighting the pressing need to develop and implement non-invasive or minimally invasive approaches to improve the diagnosis of invasive infections.

OBJECTIVES

The objectives of this article are to explore the notable features, clinical utility, and constraints associated with the detection of microbial circulating cell-free DNA (mcfDNA) as a minimally invasive diagnostic tool for infectious diseases.

CONTENT

The mcfDNA detection provides an opportunity to identify micro-organisms in the blood of a patient. It is especially beneficial in immunocompromised patients where invasive sampling is not possible or where repeated cultures are negative. This review will discuss the applications and constraints of detecting mcfDNA for diagnosing infections and the various platforms available for its detection.

Impact of cell-free DNA fungal polymerase chain reaction panels on healthcare-associated infection mould investigations

Launch of in-house sensitive cell-free deoxyribonucleic acid (cfDNA) mould polymerase chain reaction (PCR) assays increased detection of moulds meeting suspected healthcare-associated infection (HAI) criteria. Definition was based on time from admission and mould detection in culture or via molecular methods. We created a modified mould HAI algorithm incorporating clinical context into the case definition, which allowed for better capture of possible mould HAIs, decreased number of investigations, and improved utilization of Infection Prevention and Control (IPC) resources.

Utility of Plasma Microbial Cell-Free DNA Whole-Genome Sequencing for Diagnosis of Invasive Aspergillosis in Patients With Hematologic Malignancy or COVID-19

BACKGROUND

We evaluated the clinical accuracy and utility of whole-genome sequencing (WGS) of plasma microbial cell-free DNA (cfDNA) as a novel noninvasive method in diagnosing invasive aspergillosis (IA) in patients with hematologic malignancy (HM) or coronavirus disease 2019 (COVID-19).

METHODS

Adults with HM or COVID-19 and suspected IA were recruited. IA cases were retrospectively diagnosed according to EORTC/MSG definitions and ECMM/ISHAM criteria for HM and COVID-19 patients, respectively. The results of cfDNA WGS were compared with the conventional diagnosis.

RESULTS

Microbial cfDNA WGS was performed 53 times from 41 participants (19 from HM, 16 from COVID-19, and 7 from the control group). In participants with HM, Aspergillus cfDNA was detected in 100% of proven IA and 91.7% of probable IA cases. In participants with COVID-19, 50.0% of probable IA were positive for Aspergillus in cfDNA WGS. Concordance between Aspergillus cfDNA detection and proven/probable IA conventional diagnosis was significantly higher in participants with HM than in those with COVID-19. IA diagnosed using EORTC/MGS definitions showed significantly high concordance between Aspergillus cfDNA detection and proven/probable IA.

CONCLUSIONS

Aspergillus cfDNA detection strongly correlated with proven/probable IA diagnosed using EORTC/MSG definitions and could be used as an additional diagnostic tool for IA.

Diagnosis and monitoring of virus-associated cancer using cell-free DNA

Viral-associated cancers are a distinct group of malignancies with a unique pathogenesis and epidemiology. Liquid biopsy is a minimally invasive way to identify tumor-associated abnormalities in blood derivatives, such as plasma, to guide the diagnosis, prognosis, and treatment of patients with cancer. Liquid biopsy encompasses a multitude of circulating analytes with the most extensively studied being cell-free DNA (cfDNA). In recent decades, substantial advances have been made toward the study of circulating tumor DNA in nonviral-associated cancers. Many of these observations have been translated to the clinic to improve the outcomes of patients with cancer. The study of cfDNA in viral-associated cancers is rapidly evolving and reveals tremendous potential for clinical applications. This review provides an overview of the pathogenesis of viral-associated malignancies, the current state of cfDNA analysis in oncology, the current state of cfDNA analysis in viral-associated cancers, and perspectives for the future of liquid biopsies in viral-associated cancers.

Accuracy of Pneumocystis jirovecii Plasma Cell-Free DNA PCR for Noninvasive Diagnosis of Pneumocystis Pneumonia

Pneumocystis pneumonia (PCP) caused by Pneumocystis jirovecii is a serious infection in immunocompromised hosts which requires prompt diagnosis and treatment. The recommended specimen for diagnosis of PCP is bronchoalveolar lavage (BAL) fluid, which is invasive and may not be possible in unstable patients. The aim of this study was to evaluate the accuracy of noninvasive P. jirovecii plasma cell-free DNA (cfDNA) PCR using recently optimized preanalytical and analytical methods. Adult patients undergoing clinical testing for PCP with direct fluorescent antibody stain (DFA), respiratory PCR, and/or β-d-glucan were included in this study. Sensitivity and specificity P. jirovecii plasma cfDNA PCR was determined in PCP suspects categorized as proven and probable. A total of 149 patients were included in this study, of which 10 had proven and 27 had probable PCP. Most patients (95.9%, 143/149) were immunocompromised, including hematological malignancies (30.1%), bone marrow transplant (11.2%), solid organ transplantation (47.6%), and HIV/AIDS (4.2%). P. jirovecii plasma cfDNA PCR showed sensitivity and specificity of 100% (10/10; 95% confidence interval [CI], 69.2 to 100) and 93.4% (127/136; 95% CI, 87.8 to 96.9), and 48.6% (18/37; 95% CI, 31.9 to 65.6) and 99.1% (108/109; 95% CI, 94.9 to 100) in proven and proven/probable cases, respectively. P. jirovecii cell-free DNA PCR was similar in sensitivity but with substantially improved specificity over β-d-glucan (sensitivity, 60.0% [18/30; 95% CI, 40.6 to 77.3]); specificity, 66.7% [22/33; 95% CI, 48.2 to 82.0]) in patients with proven/probable PCP. Plasma cfDNA PCR offers a noninvasive testing option for early and accurate diagnosis of PCP, particularly in patients who cannot tolerate bronchoscopy.

An overview of using fungal DNA for the diagnosis of invasive mycoses

INTRODUCTION

Fungal PCR has undergone considerable standardization and together with the availability of commercial assays, external quality assessment schemes and extensive performance validation data, is ready for widespread use for the screening and diagnosis of invasive fungal disease (IFD).

AREAS COVERED

Drawing on the experience and knowledge of the leads of the various working parties of the Fungal PCR initiative, this review will address general considerations concerning the use of molecular tests for the diagnosis of IFD, before focussing specifically on the technical and clinical aspects of molecular testing for the main causes of IFD and recent technological developments.

EXPERT OPINION

For infections caused by Aspergillus, Candida and Pneumocystis jirovecii, PCR testing is recommended, combination with serological testing will likely enhance the diagnosis of these diseases. For other IFD (e.g. Mucormycosis) molecular diagnostics, represent the only non-classical mycological approach towards diagnoses and continued performance validation and standardization has improved confidence in such testing. The emergence of antifungal resistance can be diagnosed, in part, through molecular testing. Next-generation sequencing has the potential to significantly improve our understanding of fungal phylogeny, epidemiology, pathogenesis, mycobiome/microbiome and interactions with the host, while identifying novel and existing mechanisms of antifungal resistance and novel diagnostic/therapeutic targets.

Reverse-transcription PCR increases sensitivity of broad-range fungal detection in bronchoalveolar lavage fluid

Broad-range PCR targeting 28S D1-D2 ribosomal DNA (rDNA) identifies numerous fungi but has limited sensitivity in clinical specimens. Ribosomal RNA (rRNA) vastly outnumbers rDNA, suggesting reverse transcription (RT)-PCR could improve detection. Among contrived samples, RT-PCR decreased 28S PCR cycle threshold values by 10--12 cycles and lowered the limit of detection > 2000-fold. Among 32 bronchoalveolar lavage specimens, RT-PCR detected 12/15 (80%) fungal PCR- or culture-positive specimens, versus 6/12 (50%) by 28S PCR, 9/12 (75%) by any fungal PCR, and 13/15 (87%) by culture. RT-PCR newly identified fungi in 4/17 (24%) PCR- and culture-negative specimens. RT substantially increased 28S PCR sensitivity overall.

LAY SUMMARY

Fungal infection remains difficult to diagnose in the laboratory. Here, we have shown that detecting ribosomal RNA and DNA, rather than only ribosomal DNA, in a broad range fungal assay results in a significant enhancement in the ability to detect and identify fungal pathogens in clinical samples.

Molecular Diagnosis of Yeast Infections

PURPOSE OF REVIEW

The use of molecular tests to aid the diagnosis of invasive yeast infection, in particular invasive candidosis, has been described for over two decades, yet widespread application is limited, and diagnosis remains heavily dependent on classical microbiology. This article will review developments from the past decade in attempt to build on existing knowledge. It will highlight clinical performance and limitations while reviewing developments on recognized procedures; it will also provide insight into novel approaches incorporated in response to clinical demand (e.g. C. auris and antifungal resistance) or technological advances (e.g. next-generation sequencing).

RECENT FINDINGS

Limited methodological standardization and, until recently, unavailability of commercial options have hindered the integration of molecular diagnostics for yeasts. The development of certain, novel commercial methods has received considerable evaluation allowing a greater understanding of individual assay performance, but widespread multicentre evaluation of most commercial kits is lacking. The detection of emerging pathogens (e.g. C. auris) has been enhanced by the development of molecular tests. Molecular methods are providing a better understanding of the mycobiome, mechanisms of resistance and epidemiology/phylogeny.

SUMMARY

Despite over two decades of use, the incorporation of molecular methods to enhance the diagnosis of yeast infections remains limited to certain specialist centres. While the development of commercial tests will provide stimulus for broader application, further validation and reduced costs are required. Over the same period of time, Aspergillus PCR has become more widely accepted driven by international efforts to standardize methodology; it is critical that yeast PCR follows suit. Next-generation sequencing will provide significant information on the mycobiome, antifungal resistance mechanism and even broad-range detection directly from the specimen, which may be critical for the molecular detection of yeasts other than Candida species, which is currently limited.