Fungal biomarker turn-around-time (TAT) and antifungal stewardship: how long is too long?

Author:

Clare Logan1, Jonathan Youngs1, Hassan Al-Ghusein1, Silke Schelenz2, Tihana Bicanic1

Author address:

1St George’s Hospital, London.
2Royal Brompton Hospital, London

Full conference title:

Federation of Infectious Societies Conference 2018

Date: 12 December 2019

Abstract:

Introduction: Fungal biomarkers are an important tool for antifungal stewardship. Optimising antifungal drug use is essential to limit exposure to toxic drugs, curtail the emergence of fungal resistance and minimise unnecessary drug expenditure. Additionally, fungal biomarkers are important adjuncts to radiological and microbiological investigation in the diagnosis of invasive fungal infection (IFI), where, given the high mortality, timely diagnosis is essential.

The aim of this study was to look at the turn-around-time of fungal biomarkers at two large London teaching hospitals, St George’s Hospital (SGH)  and the Royal Brompton hospitals (RBH), to assess whether in a real-world setting, results are available to clinicians within a meaningful timeframe to assist diagnosis and impact on antifungal stewardship.

Methods: Samples sent for galactomannan (GM) and Beta-D-glucan (BDG) at SGH (01/2010-07/2018) and RBH (01/2014-07/2018) were identified from the respective microbiology databases. The turn-around time (TAT) was defined as the number of days between the date of receipt of specimen in the laboratory to the date of result authorisation. Specimen type, source (ICU, non ICU inpatient, outpatient clinic) and result (positive, indeterminate or negative) were also analysed.   Analyses were conducted in Microscoft Excel 2013 and GraphPad Prism v7.

Results: In total, 3199 samples were sent for GM testing (2229 at RBH, 970 at SGH). All SGH GM samples are sent to the Bristol Mycology Reference Laboratory (MRL) with a median (Interquartile range (IQR)) TAT of 13 days (11-17) days. RBH GM samples prior to August 2015 were also sent to the MRL, with a median (IQR) TAT of 8 (5-14) days (Mann Witney p<0.0001, comparison with SGH TAT). After August 2015, RBH performed the assay in-house, halving the median TAT to 4 (2-5) days (Mann Witney p<0.0001 pre- and post- in house testing comparison for RBH).

For BDG testing, a total of 635 samples were sent with TAT data (RBH=610, SGH=25).  Prior to June 2017 at RBH, samples were sent to the MRL and median (IQR) TAT was 6 (3-7) days. From June 2017, RBH samples were sent to Kings College Hospital, London (KCH) and the median (IQR) TAT reduced to 3 (2-6) days (Mann Witney p<0.0001 pre- and post- KCH send-away comparison for RBH). SGH sent away all samples to the MRL with median (IQR) TAT of 12 days (9-14) days.

Data on specimen type, source and result will also be presented.

Discussion: A median turn-around time of 1-2 weeks significantly devalues the use of fungal biomarkers for both diagnosis of IFI and antifungal stewardship, hindering clinical decision-making. Our results confirm that sending away biomarkers to a geographically distant reference lab prolongs TAT in comparison to having the tests done locally or in-house, with RBH, halving the TAT for GM and BDG by performing it in-house and at a local laboratory respectively.

However it is also apparent that not all TAT prolongation issues are secondary to samples being sent away to Bristol, as shown by the comparison between SGH and RBH TAT for the same tests done at MRL, suggestive of internal logistical issues at SGH laboratory.

With antifungal stewardship high up on the agenda of the NHS England Improving Value Project and a planned rollout of an antifungal CQUIN, guidance and incentives are needed not only around antifungal prescribing but also the performance of fungal diagnostics and recommended minimum TAT. We propose that a TAT of 3-5 days would maximise the diagnostic and antifungal stewardship benefits of fungal biomarkers.  Greater harmonisation and the creation of regional diagnostic hubs will be required to achieve this goal.

Abstract Number: 184

Conference Year: 2018

Link to conference website:

Link Conference abstract: 

FIS 2018

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