title: Defining ELISpot cut-offs from unreplicated test and control wells.
abstract: In the absence of replication of wells, empirical criteria for enzyme-linked immunospot (ELISpot) positivity use fixed differences or ratios between spot forming units (SFU) counts between test and control. We propose an alternative approach which first identifies the optimally variance-stabilizing transformation of the SFU counts, based on the Bland-Altman plot of the test and control wells. The second step is to derive a positivity threshold from the difference in between-plate distribution functions of the transformed test and control SFU counts. This method is illustrated using 1309 assay results from a cohort study of influenza in Vietnam in which some, but not all, of the peptide pools have clear tendencies for SFU counts to be higher in test than control wells.
authors.affiliation: London School of Hygiene and Tropical Medicine, London, United Kingdom. neal.alexander@lshtm.ac.uk
authors.forename: Neal
authors.initials: N
authors.lastname: Alexander
authors.forename: Annette
authors.initials: A
authors.lastname: Fox
authors.forename: Vu Thi Kim
authors.initials: VT
authors.lastname: Lien
authors.forename: Tao
authors.initials: T
authors.lastname: Dong
authors.forename: Laurel Yong-Hwa
authors.initials: LY
authors.lastname: Lee
authors.forename: Nguyen Le Khanh
authors.initials: Nle K
authors.lastname: Hang
authors.forename: Le Quynh
authors.initials: le Q
authors.lastname: Mai
authors.forename: Peter
authors.initials: P
authors.lastname: Horby
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D058501:Enzyme-Linked Immunospot Assay / Q000379:methods*; D006801:Humans; D007251:Influenza, Human / Q000276:immunology; D008875:Middle Aged; D010455:Peptides / Q000737:chemistry; D014744:Vietnam; D055815:Young Adult
chemical_list: D010455:Peptides