title: Evaluation of the time resolved fluorescence immunoassay (TRFIA) for the detection of varicella zoster virus (VZV) antibodies following vaccination of healthcare workers.
abstract: Determination of varicella zoster virus (VZV) immunity in healthcare workers without a history of chickenpox is important for identifying those in need of vOka vaccination. Post immunisation, healthcare workers in the UK who work with high risk patients are tested for seroconversion. To assess the performance of the time-resolved fluorescence immunoassay (TRFIA) for the detection of antibody in vaccinated as well as unvaccinated individuals, a cut-off was first calculated. VZV-IgG specific avidity and titres six weeks after the first dose of vaccine were used to identify subjects with pre-existing immunity among a cohort of 110 healthcare workers. Those with high avidity (≥ 60%) were considered to have previous immunity to VZV and those with low or equivocal avidity (<60%) were considered naive. The former had antibody levels ≥ 400 mIU/mL and latter had levels < 400 mIU/mL. Comparison of the baseline values of the naive and immune groups allowed the estimation of a TRFIA cut-off value of > 130 mIU/mL which best discriminated between the two groups and this was confirmed by ROC analysis. Using this value, the sensitivity and specificity of TRFIA cut-off were 90% (95% CI 79-96), and 78% (95% CI 61-90) respectively in this population. A subset of samples tested by the gold standard Fluorescence Antibody to Membrane Antigen (FAMA) test showed 84% (54/64) agreement with TRFIA.
authors.affiliation: Centre of Immunology and Infectious Diseases, Blizard Institute of Cell and Molecular Science, Bart's and the London School of Medicine and Dentistry, Queen Mary University of London, 4 Newark St, Whitechapel, London E12AT, UK.
authors.forename: S L R
authors.initials: SL
authors.lastname: McDonald
authors.forename: P A C
authors.initials: PA
authors.lastname: Maple
authors.forename: N
authors.initials: N
authors.lastname: Andrews
authors.forename: K E
authors.initials: KE
authors.lastname: Brown
authors.forename: K L
authors.initials: KL
authors.lastname: Ayres
authors.forename: F T
authors.initials: FT
authors.lastname: Scott
authors.forename: M
authors.initials: M
authors.lastname: Al Bassam
authors.forename: A A
authors.initials: AA
authors.lastname: Gershon
authors.forename: S P
authors.initials: SP
authors.lastname: Steinberg
authors.forename: J
authors.initials: J
authors.lastname: Breuer
mesh_terms: D000328:Adult; D000914:Antibodies, Viral / Q000097:blood*; D000915:Antibody Affinity / Q000276:immunology; D002644:Chickenpox / Q000517:prevention & control*; D005260:Female; D015200:Fluoroimmunoassay / Q000592:standards*; D006282:Health Personnel; D014645:Herpesvirus 3, Human / Q000276:immunology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D012680:Sensitivity and Specificity; D014611:Vaccination
chemical_list: D000914:Antibodies, Viral