Variability of the IFN-γ ELISpot assay in the context of proficiency testing and bridging studies.
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Assays that assess cellular mediated immune responses performed under Good Clinical Laboratory Practice (GCLP) guidelines are required to provide specific and reproducible results. Defined validation procedures are required to establish the Standard Operating Procedure (SOP), include pass and fail criteria, as well as implement positivity criteria. However, little to no guidance is provided on how to perform longitudinal assessment of the key reagents utilized in the assay. Through the External Quality Assurance Program Oversight Laboratory (EQAPOL), an Interferon-gamma (IFN-γ) Enzyme-linked immunosorbent spot (ELISpot) assay proficiency testing program is administered. A limit of acceptable within site variability was estimated after six rounds of proficiency testing (PT). Previously, a PT send-out specific within site variability limit was calculated based on the dispersion (variance/mean) of the nine replicate wells of data. Now an overall 'dispersion limit' for the ELISpot PT program within site variability has been calculated as a dispersion of 3.3. The utility of this metric was assessed using a control sample to calculate the within (precision) and between (accuracy) experiment variability to determine if the dispersion limit could be applied to bridging studies (studies that assess lot-to-lot variations of key reagents) for comparing the accuracy of results with new lots to results with old lots. Finally, simulations were conducted to explore how this dispersion limit could provide guidance in the number of replicate wells needed for within and between experiment variability and the appropriate donor reactivity (number of antigen-specific cells) to be used for the evaluation of new reagents. Our bridging study simulations indicate using a minimum of six replicate wells of a control donor sample with reactivity of at least 150 spot forming cells per well is optimal. To determine significant lot-to-lot variations use the 3.3 dispersion limit for between and within experiment variability.
Published Version (Please cite this version)10.1016/j.jim.2016.03.004
Publication InfoRountree, Wes; Berrong, Mark; Sanchez, Ana M; Denny, Thomas N; & Ferrari, Guido (2016). Variability of the IFN-γ ELISpot assay in the context of proficiency testing and bridging studies. J Immunol Methods, 433. pp. 69-76. 10.1016/j.jim.2016.03.004. Retrieved from https://hdl.handle.net/10161/12062.
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Professor in Medicine
Thomas N. Denny, MSc, M.Phil, is the Chief Operating Officer of the Duke Human Vaccine Institute (DHVI) and the Center for HIV/AIDS Vaccine Immunology (CHAVI), and a Professor of Medicine in the Department of Medicine at Duke University Medical Center. He is also an Affiliate Member of the Duke Global Health Institute. He has recently been appointed to the Duke University Fuqua School of Business Health Sector Advisory Council. Previously, he was an Associate Professor of Pathology, Laboratory M
Associate Professor of Surgery
The activities of the Ferrari Laboratory are based on both independent basic research and immune monitoring studies. The research revolves around three main areas of interest: class I-mediated cytotoxic CD8+ T cell responses, antibody-dependent cellular cytotoxicity (ADCC), gene expression in NK and T cellular subsets upon infection with HIV-1. With continuous funding over the last 11 years from the NIH and Bill & Melinda Gates Foundation along with many other productive collaborations wi
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