Elsevier

Journal of Clinical Virology

Volume 96, November 2017, Pages 89-93
Journal of Clinical Virology

Full length article
A European multi-centre External Quality Assessment (EQA) study on phenotypic and genotypic methods used for Herpes Simplex Virus (HSV) drug resistance testing

https://doi.org/10.1016/j.jcv.2017.10.002Get rights and content

Highlights

  • •

    First European EQA scheme for Herpes Simplex Virus phenotypic and genotypic drug resistance.

  • •

    Broad data concordance among participating labs was observed despite diverse testing strategies.

  • •

    Points of difference able to inform future schemes and help improve testing protocols.

Abstract

Background

Herpes Simplex Virus (HSV) drug resistance is a significant public health concern among immunocompromised individuals. Phenotypic assays are considered the gold standard method for detecting HSV drug resistance. However, plaque reduction assays (PRAs) are technically demanding, often with long turnaround times of up to four weeks. In contrast, genotypic tests can be performed within a few days.

Objectives

The development and coordination of the first European External Quality Assessment (EQA) study to evaluate phenotypic and genotypic methods used for HSV drug resistance testing in specialised reference laboratories.

Study design

Four HSV-1 or HSV-2 strains with different antiviral susceptibility profiles were isolated from clinical samples. Isolates were quantified by qPCR, and aliquoted in culture medium. One isolate was distributed at two dilutions to help assess assay sensitivity. The panel was distributed to five European centres with a six-week deadline for the return of phenotypic and genotypic results, together with clinical reports.

Results

Four out of five participating labs returned results by the deadline. Limited results were later available from the fifth lab. Phenotypic and genotypic data were largely, but not completely, concordant. An unusual resistance profile shown by one of the samples was explained by the detection of a mixed virus population after extensive further investigation by one of the centres.

Conclusions

Discordant clinical outputs reflecting the diversity of phenotypic methodologies demonstrated the utility of this exercise. With emerging genotypic technologies looking to supplant phenotyping, there is a need for curated public databases, accessible interpretation tools and standardised control materials for quality management. By establishing a network of testing laboratories, we hope that this EQA scheme will facilitate ongoing progress in this area.

Section snippets

Background

Herpes Simplex Virus type 1 (HSV-1) and type 2 (HSV-2) are responsible for recurrent orofacial and genital infections. The primary infection is usually self-limiting and is followed by establishment of long-term latency in the ganglia of sensory nerves from where it can recur upon alteration of the immune system. Neonates who are born to mothers with active HSV may acquire the virus and develop life-threatening conditions. Depending on extent of infection, neonatal herpes can be categorised

Objectives

To co-ordinate the first European HSV EQA scheme, enabling:

  • (i)

    the evaluation of phenotypic and genotypic methods used for HSV drug resistance testing in specialised laboratories

  • (ii)

    the comparison of genotypic, phenotypic and clinical reports between participating laboratories

  • (iii)

    the establishment of a network of collaborating laboratories for ongoing quality assurance to be established

Study design

The testing panel was prepared from UK clinical samples submitted between 2010 and 2013 to the Antiviral Unit (AVU), Virus Reference Department (VRD), Public Health England (PHE), Colindale (see Table 1) and comprised two HSV type 1 strains (reference number: HSV-EQA-2016-A and HSV-EQA-2016-C) and two HSV type 2 strains (HSV-EQA-2016-B, and HSV-EQA-2016-D) with a range of antiviral susceptibility profiles. Sample HSV-EQA-2016-E comprised a 10 x dilution of sample HSV-EQA-2016-B in order to help

Results

Four out of five laboratories (coded 1 through 4 to preserve anonymity) returned data sets within the allotted turnaround time. The fifth centre returned partial data sets later, which were not included in the analysis.

Discussion

Currently, the gold standard method for detecting HSV resistance is a phenotypic assay, which requires specialised laboratory experience and is technically demanding with long turnaround times of up to three to four weeks. In contrast, genotypic tests can be performed within a few days and can be easily set up by most clinical microbiology laboratories with molecular experience, but rely on data generated by phenotyping. ISO15189 standard 5.6.3 requires that laboratories participate in an

Conflict of interest

The authors have no conflict of interest to declare.

Acknowledgements

The authors would like to thank Mrs Ellen De Waegenaere and Mr Seppe Kelchtermans from the Rega Institute for excellent technical assistance.

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