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However, precision, also called \u201cerror of assay (EoA)\u201d, in GIA readouts and the source of EoA has not been evaluated systematically.<\/jats:p><\/jats:sec><jats:sec><jats:title>Methods<\/jats:title><jats:p>In the Main GIA experiment, 4 different cultures of<jats:italic>P. falciparum<\/jats:italic>3D7 parasites were prepared with red blood cells (RBC) collected from 4 different donors. For each culture, 7 different anti-RH5 Ab (either monoclonal or polyclonal Ab) were tested by GIA at two concentrations on three different days (168 data points). To evaluate sources of EoA in % inhibition in GIA (%GIA), a linear model fit was conducted including donor (source of RBC) and day of GIA as independent variables. In addition, 180 human anti-RH5 polyclonal Ab were tested in a Clinical GIA experiment, where each Ab was tested at multiple concentrations in at least 3 independent GIAs using different RBCs (5,093 data points). The standard deviation (sd) in %GIA and in GIA<jats:sub>50<\/jats:sub>(Ab concentration that gave 50%GIA) readouts, and impact of repeat assays on 95% confidence interval (95%CI) of these readouts was estimated.<\/jats:p><\/jats:sec><jats:sec><jats:title>Results<\/jats:title><jats:p>The Main GIA experiment revealed that the RBC donor effect was much larger than the day effect, and an obvious donor effect was also observed in the Clinical GIA experiment. Both %GIA and log-transformed GIA<jats:sub>50<\/jats:sub>data reasonably fit a constant sd model, and sd of %GIA and log-transformed GIA<jats:sub>50<\/jats:sub>measurements were calculated as 7.54 and 0.206, respectively. Taking the average of three repeat assays (using three different RBCs) reduces the 95%CI width in %GIA or in GIA<jats:sub>50<\/jats:sub>measurements by\u2009~\u2009half compared to a single assay.<\/jats:p><\/jats:sec><jats:sec><jats:title>Conclusions<\/jats:title><jats:p>The RBC donor effect (donor-to-donor variance on the same day) in GIA was much bigger than the day effect (day-to-day variance using the same donor\u2019s RBC) at least for the RH5 Ab evaluated in this study; thus, future GIA studies should consider the donor effect. In addition, the 95%CI for %GIA and GIA<jats:sub>50<\/jats:sub>shown here help when comparing GIA results from different samples\/groups\/studies; therefore, this study supports future malaria blood-stage vaccine development.<\/jats:p><\/jats:sec>","DOI":"10.1186\/s12936-023-04591-6","type":"journal-article","created":{"date-parts":[[2023,5,19]],"date-time":"2023-05-19T05:01:55Z","timestamp":1684472515000},"update-policy":"https:\/\/doi.org\/10.1007\/springer_crossmark_policy","source":"Crossref","is-referenced-by-count":17,"title":["Assessment of precision in growth inhibition assay (GIA) using human anti-PfRH5 antibodies"],"prefix":"10.1186","volume":"22","author":[{"given":"Kazutoyo","family":"Miura","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Ababacar","family":"Diouf","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Michael P.","family":"Fay","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jordan R.","family":"Barrett","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Ruth O.","family":"Payne","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Ally I.","family":"Olotu","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Angela M.","family":"Minassian","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Sarah E.","family":"Silk","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Simon J.","family":"Draper","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Carole A.","family":"Long","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"297","published-online":{"date-parts":[[2023,5,19]]},"reference":[{"key":"4591_CR1","doi-asserted-by":"publisher","first-page":"534","DOI":"10.1038\/nature10606","volume":"480","author":"C Crosnier","year":"2011","unstructured":"Crosnier C, Bustamante LY, Bartholdson SJ, Bei AK, Theron M, Uchikawa M, et al. 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The VAC063 study was reviewed and approved by the UK NHS Research Ethics Service (Oxfordshire Research Ethics Committee A, Ref 16\/SC\/0345) and by the UK Medicines and Healthcare products Regulatory Agency (Ref 21584\/ 0362\/001\u20130011). The VAC070 study was approved by the Oxford Tropical Research Ethics Committee (OxTREC, reference 29\u201317), the Ifakara Health Institute Institutional Review Board (IHI-IRB, reference 20\u20132017), the Tanzanian National Health Research Ethics Sub-Committee \/ National Institute for Medical Research (NatHREC\/NIMR, reference NIMR\/HQ\/R8a\/Vol. IX\/2643), and the Tanzania Food and Drug Authority (TFDA, now known as the Tanzania Medicines and Medical Devices Authority, TMDA, reference TFDA0017\/CTR\/0015\/3).In all three trials, written informed consent was obtained from study participants or the parents or guardians of children aged\u2009<\u200918\u00a0years (in the VAC070 study each participant signed or thumb-printed an informed consent form at the in-person screening visit).","order":2,"name":"Ethics","group":{"name":"EthicsHeading","label":"Ethics approval and consent to participate"}},{"value":"Not applicable.","order":3,"name":"Ethics","group":{"name":"EthicsHeading","label":"Consent for publication"}},{"value":"S.J.D. is named inventors on patent applications relating to RH5 and\/or other malaria vaccines and immunization regimens. A.M.M. has an immediate family member who is an inventor on patents relating to RH5 and\/or other malaria vaccines and immunization regimens.","order":4,"name":"Ethics","group":{"name":"EthicsHeading","label":"Competing interests"}}],"article-number":"159"}}