The European Aspergillus PCR Iniative (EACPRI) – Where do we stand?

Ref ID: 19462

Author:

P. L. White

Author address:

PHW Microbiology Cardiff, United Kingdom

Full conference title:

6th Trends in Medical Mycology 2013

Date: 11 October 2014

Abstract:

Aspergillus PCR has a come a long way since first described in
19931. It has evolved to encompass real-time PCR technology and
automation, but taken over a decade to standardise procedures,
develop an international PCR calibrator, commercial options and
external quality control (QC) programmes. Consequently, evidence
concerning clinical applicability and utility is sparse. Now, twenty
years later, it must be asked whether PCR is sufficiently standardised
and evaluated to allow incorporation into the EORTC/MSG definitions
of invasive fungal disease as well as routine use.
In 2006, the European Aspergillus PCR Initiative (EAPCRI: www.
eapcri.eu) was formed after recognising, that despite numerous publi-
cations highlighting the benefits of Aspergillus PCR testing, methodo-
logical heterogeneity and the lack of a standardised, quality
controlled commercial alternative prevented widespread use. The
consensus was that a screening strategy was paramount for diseases
of relatively low incidence, such as invasive aspergillosis (IA). Hence
the negative predictive value (NPV) should be sufficiently high to
exclude IA in patients that were consistently PCR negative. To
achieve this, a low analytical false negativity rate, i.e. high sensitiv-
ity, and frequent testing were a prerequisite, and blood samples were
favoured as they are easy to obtain at regular, frequent intervals. By
contrast, the testing of invasive samples (BAL or tissue) is reserved
for confirming a diagnosis of IA.
The EAPCRI has, through the distribution of QC panels, deter-
mined the optimal processes for Aspergillus PCR testing of both serum
and whole blood (WB), and showed that the nucleic acid extraction,
rather than PCR amplification, is critical. Recommendations for test-
ing both sample types and for PCR amplification have been pub-
lished, which if followed, provide the analytical performance required
for testing these samples2-4. Recently, a clinical evaluation of serum
and WB PCR testing using EAPCRI recommendations showed a simi-
lar performance overall. The increase in sensitivity associated with
testing WB was offset by the reduction in specificity and technical
complexity of testing this sample type5. The simplicity in testing
serum is a clear advantage especially if PCR is to attain widespread
use, as it permits incorporation into routine molecular diagnostic lab-
oratories and commercial options for testing this sample type are
available.
The latest EAPCRI studies focussed on testing plasma with the
hypothesis that the formation of the clot leading to serum may be
detrimental to the amount of available target. Studies were per-
formed to determine the effect on initial sample processing and the
efficacy of molecular methods when testing serum and plasma.
Another study focussed on analytical specificity (detection range/
cross reactivity) of Aspergilus PCR protocols currently in routine use.
The results of these investigations will be presented along with a pro-
posed algorithm for the Aspergillus PCR testing of blood samples.
In summary, recommendations are now available for the Aspergillus
PCR testing of WB, serum and plasma. If followed, they will pro-
vide sufficient analytical sensitivity for PCR to be integrated into a
screening algorithm where consistent negativity can exclude IA. In
line with other PCR assays an international PCR standard for Aspergillus
PCR will provide a consistent and standardised limit of detec-
tion for all PCR methods to be measured against6. Independent QC
panels for Aspergillus PCR are now available for centres to blindly
assess performance annually. The availability of commercial assays
will provide the same quality assurance and a standard approach
enjoyed by commercial tests for galactomannan. In short, Aspergillus
PCR has the same infra-structure in place as most molecular assays targeting other pathogens that are widely and routinely accepted.
Recent clinical trials of diagnostic driven approaches incorporating
PCR testing have shown excellent clinical validity and utility7,8. Con-
sequently, the time has come for PCR to be accepted at least as
another tool essential to improve the management of patients at risk
of IA and take its place in the EORTC/MSG definitions.

Abstract Number: w12.2

Conference Year: 2013

Link to conference website: NULL

New link: NULL

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