Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Researchers identify tests to diagnose invasive aspergillosis with 100 percent accuracy

14.08.2014

Early, more accurate detection of this potentially deadly fungus can improve patient outcomes, according to new report in The Journal of Molecular Diagnostics

The fungal infection invasive aspergillosis (IA) can be life threatening, especially in patients whose immune systems are weakened by chemotherapy or immunosuppressive drugs. Despite the critical need for early detection, IA remains difficult to diagnose.

A study in The Journal of Molecular Diagnostics compared three diagnostic tests and found that the combination of nucleic acid sequence-based amplification (NASBA) and real-time quantitative PCR (qPCR) detects aspergillosis with 100% accuracy.

IA is caused by the fungus Aspergillus fumigatus, which is considered by many pathologists to be the world's most harmful mold. "Traditional diagnostic methods, such as culture and histopathology of infected tissues, often fail to detect Aspergillus," comments lead investigator Yun Xia, PhD, of the First Affiliated Hospital of Chongqing Medical University, Chongqing, China.

In this retrospective study, scientists evaluated the diagnostic performance of two nucleic acid amplification assays (qPCR and NASBA) and one antigen detection method (galactomannan enzyme-linked immunosorbent assay [GM-ELISA]) using blood samples collected from 80 patients at high risk of IA. Of the 80 patients, 42.5% had proven or probable IA. The patients came from intensive care, hematology, neurology, nephrology, geriatrics, and other hospital departments.

The tests were evaluated singly and in combination. Individually, NASBA had the highest sensitivity (76.47%) whereas qPCR offered the highest specificity (89.13%). NASBA also was the test that best indicated that a patient did not have the infection (negative predictive value). NASBA and qPCR each had a high Youden index, a measure of the effectiveness of a diagnostic marker.

Combining the tests improved the outcomes. The combination of NASBA and qPCR led to 100% specificity and 100% positive predictive value (the probability that subjects truly have the infection).

"Because each test has advantages and disadvantages, a combination of different tests may be able to provide better diagnostic value than is provided by a single test," says Dr. Xia. The combination of NASBA and qPCR should be useful in excluding IA in suspect cases, thus reducing both suffering and expense for immunocompromised patients. On the other hand, the combination of NASBA and qPCR could be more suitable for screening patients suspected of infection, because this assay had the highest sensitivity."

The authors note that NASBA offers the advantages of rapid amplification (90 minutes) and simple operation with low instrument cost compared with qPCR and GM-ELISA. They caution that although GM-ELISA is widely and routinely used for aspergillosis diagnosis, this study indicates that it had low sensitivity (52.94%) with reasonable specificity (80.43%), making it "inferior to both NASBA and qPCR."

The A. fumigatus mold is ubiquitous in the environment and is found on decaying plant matter. For healthy individuals exposure to the fungus can be inconsequential, but it can cause significant morbidity and mortality for those with compromised immune systems, including patients who have undergone organ transplants or have advanced AIDS. Even patients with more modest immune impairments, such as diabetes, poor nutrition, steroid use, or lung disease, can become severely infected. Symptoms may include fever, cough, difficulty breathing, chest pain, seizures, and focal neurological problems.

The criteria for high risk for IA included high (1,3)-β-D-glucan levels (>60 pg/mL), immunocompromised status, and one of six conditions (recipient of an allogeneic stem cell transplant, hematological disease, severe immunodeficiency, prolonged use of corticosteroids, fever or chest infiltrate unresponsive to routine antibiotics, or radiological indication of fungal disease). Patients did not receive any antifungal therapy until after blood samples were collected.

The first test was the measurement of GM, a polysaccharide component of the fungal cell wall, which can be released into serum and bronchoalveolar lavage fluid during infection. GM was measured using a commercially available ELISA kit (Platelia Aspergillus; Bio-Rad Laboratories, Hercules, CA). In this study, a GM index (GMI) of 0.5 was used.

The second test was an Aspergillus DNA extraction and real-time qPCR assay. The DNA was extracted from plasma using a QIAamp blood mini kit (Qiagen, Hilden, Germany). The purified DNA was then amplified by an Aspergillus genus-specific qPCR assay using SYBR Green chemistry and primers targeting the 28S rRNA gene. The lower limit of detection was empirically determined to be 10 colony-forming units of Aspergillus conidia per reaction.

The third test was an Aspergillus RNA extraction and NASBA assay. Total RNA was extracted from plasma using a blood/liquid sample total RNA rapid extraction kit (BioTeke, Beijing, China). A highly conserved 18S rRNA region specific for the Aspergillus genus was chosen as the detection target. It was then amplified using a pair of primers. Blank control, negative control (RNA extracted from patients without Aspergillus infection) and positive control (RNA extracted from Aspergillus in pure culture) were included in each run.

Eileen Leahy | Eurek Alert!
Further information:
http://www.elsevier.com

Further reports about: Aspergillus DNA Health RNA accuracy amplification combination culture extraction fungal immune invasive

More articles from Life Sciences:

nachricht New Model of T Cell Activation
27.05.2016 | Albert-Ludwigs-Universität Freiburg im Breisgau

nachricht Fungi – a promising source of chemical diversity
27.05.2016 | Leibniz-Institut für Naturstoff-Forschung und Infektionsbiologie - Hans-Knöll-Institut (HKI)

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Worldwide Success of Tyrolean Wastewater Treatment Technology

A biological and energy-efficient process, developed and patented by the University of Innsbruck, converts nitrogen compounds in wastewater treatment facilities into harmless atmospheric nitrogen gas. This innovative technology is now being refined and marketed jointly with the United States’ DC Water and Sewer Authority (DC Water). The largest DEMON®-system in a wastewater treatment plant is currently being built in Washington, DC.

The DEMON®-system was developed and patented by the University of Innsbruck 11 years ago. Today this successful technology has been implemented in about 70...

Im Focus: Computational high-throughput screening finds hard magnets containing less rare earth elements

Permanent magnets are very important for technologies of the future like electromobility and renewable energy, and rare earth elements (REE) are necessary for their manufacture. The Fraunhofer Institute for Mechanics of Materials IWM in Freiburg, Germany, has now succeeded in identifying promising approaches and materials for new permanent magnets through use of an in-house simulation process based on high-throughput screening (HTS). The team was able to improve magnetic properties this way and at the same time replaced REE with elements that are less expensive and readily available. The results were published in the online technical journal “Scientific Reports”.

The starting point for IWM researchers Wolfgang Körner, Georg Krugel, and Christian Elsässer was a neodymium-iron-nitrogen compound based on a type of...

Im Focus: Atomic precision: technologies for the next-but-one generation of microchips

In the Beyond EUV project, the Fraunhofer Institutes for Laser Technology ILT in Aachen and for Applied Optics and Precision Engineering IOF in Jena are developing key technologies for the manufacture of a new generation of microchips using EUV radiation at a wavelength of 6.7 nm. The resulting structures are barely thicker than single atoms, and they make it possible to produce extremely integrated circuits for such items as wearables or mind-controlled prosthetic limbs.

In 1965 Gordon Moore formulated the law that came to be named after him, which states that the complexity of integrated circuits doubles every one to two...

Im Focus: Researchers demonstrate size quantization of Dirac fermions in graphene

Characterization of high-quality material reveals important details relevant to next generation nanoelectronic devices

Quantum mechanics is the field of physics governing the behavior of things on atomic scales, where things work very differently from our everyday world.

Im Focus: Graphene: A quantum of current

When current comes in discrete packages: Viennese scientists unravel the quantum properties of the carbon material graphene

In 2010 the Nobel Prize in physics was awarded for the discovery of the exceptional material graphene, which consists of a single layer of carbon atoms...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Networking 4.0: International Laser Technology Congress AKL’16 Shows New Ways of Cooperations

24.05.2016 | Event News

Challenges of rural labor markets

20.05.2016 | Event News

International expert meeting “Health Business Connect” in France

19.05.2016 | Event News

 
Latest News

11 million Euros for research into magnetic field sensors for medical diagnostics

27.05.2016 | Awards Funding

Fungi – a promising source of chemical diversity

27.05.2016 | Life Sciences

New Model of T Cell Activation

27.05.2016 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>