Baharak Afshar1, David F Bibby2, Renata Piorkowska3, Natasha Ohemeng-Kumi3, Robert Snoeck4, Graciela Andrei4, Sarah Gillemot4, Florence Morfin5, Emilie Frobert5, Sonia Burrel6, David Boutolleau6, Brendan Crowley7, Jean L Mbisa3. 1. National Infection Service, Public Health England (PHE), Colindale, UK; European Public Health Microbiology Programme (EUPHEM), European Centre for Disease Prevention and Control (ECDC), Stockholm, Sweden. 2. National Infection Service, Public Health England (PHE), Colindale, UK. Electronic address: david.bibby@phe.gov.uk. 3. National Infection Service, Public Health England (PHE), Colindale, UK. 4. Rega Institute for Medical Research, KU Leuven, Leuven, Belgium. 5. Laboratory of Virology, IAI, CBN, Groupement Hospitalier Nord, F-69317 Lyon, University of Lyon and Virpath, CIRI, INSERM U1111, CNRS UMR5308, ENS Lyon, Université Claude Bernard Lyon 1, F-69372 Lyon, France. 6. AP-HP, University Hospital La Pitié-Salpêtrière - Charles Foix, National Reference Centre for Herpesviruses, Virology Department and Sorbonne Universités, UPMC Univ Paris 06, CR7, CIMI, INSERM U1135, Paris, France. 7. Microbiology Department, Central Pathology Laboratory, St James's Hospital, Dublin, Ireland.
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. Crown
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. Crown