key: cord-0715985-qq70i2k2 authors: Emmerich, P.; Murawski, C.; von Possel, R.; Oestereich, L.; Duraffour, S.; Pahlmann, M.; Struck, N. S.; Eibach, D.; Krumkamp, R.; Amuasi, J.; Maiga-Ascofare, O.; Rakotozandrindrainy, R.; Asogun, D.; Ighodalo, Y.; May, J.; Tannich, E.; Deschermeier, C. title: Limited specificity of commercially available SARS-CoV-2 IgG ELISAs in serum samples of African origin date: 2020-09-18 journal: nan DOI: 10.1101/2020.09.15.20159749 sha: 01fdb0c6d84798234dd846312070163e3f740df3 doc_id: 715985 cord_uid: qq70i2k2 Specific serological tests are mandatory for reliable SARS-CoV-2 seroprevalence studies but assay specificity may vary considerably between populations due to interference of immune responses to other pathogens. Here, we assess the false positive rates obtained with four commercially available IgG ELISAs in serum panels originating from three different African countries. Madagascar, Nigeria, Kenya, and South Sudan; in 14 other African countries (e.g. Uganda, 48 Burundi, Rwanda) clusters of cases or sporadic cases have been described (1). To correctly 49 determine the actual exposure of the population to SARS-CoV-2 and to draw reliable 50 conclusions on morbidity and case fatality rates, highly sensitive and specific serological 51 tests are mandatory. 52 Up to now, a plethora of serological tests for detection of anti-SARS-Cov-2 antibodies has 53 been developed and commercialized (2, 3). Although performance data for several of these 54 assays have been rapidly communicated by different laboratories (4-8), to our knowledge no 55 reports are available yet on the applicability of these tests on African serum panels. Here, 56 assay specificity may be challenged by previous or current infections with other pathogens; 57 in particular, hypergammaglobulinemia induced by Plasmodium infection may cause false 58 positive results in serological tests (9, 10). 59 To assess the specificities of commercially available SARS-CoV-2 IgG ELISA tests in serum 62 panels of different origin, a priori SARS-CoV-2 IgG negative serum panels (Appendix Table 63 1) collected before 2019 in African countries (Ghana: n=79, Madagascar: n=79, Nigeria: 64 n=40, comprising samples from both febrile patients and symptom-free donors), South 65 All rights reserved. No reuse allowed without permission. perpetuity. preprint (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in recomWell SARS-CoV-2 IgG ELISA (Mikrogen, Neuried, Germany) (Appendix Table 2 ). 71 Assays were performed and evaluated according to the manufacturers' instructions. To 72 quantify variation of index values determined on different days/plates (inter-assay/inter-lot 73 variation), two sera from German patients with a previous PCR-confirmed SARS-CoV-2 74 infection which were collected on day 19 post onset of symptoms and one commercially 75 available human negative control serum (Merck Millipore) were included in each test 76 run/plate. In addition, subsets of serum panels were assayed using the Wantai SARS-CoV-2 77 Ab ELISA (Wantai, Beijing, China) detecting total anti-SARS-CoV-2 Ig (Appendix Table 2 ). 78 BNITM in-house SARS-CoV-2 IgG indirect immunofluorescence testing (IIFT) was performed 79 as described previously (11). 80 While IgG ELISA specificities where good to excellent for pre-COVID-19 serum panels 81 originating from Colombia, Lao PDR, Madagascar, and Germany, increased false positive 82 rates were observed in a priori SARS-CoV-2 IgG negative sera from Ghana and Nigeria 83 ( Figure 1 , Table 1 ). False positive rates were comparable in serum samples originating from 84 febrile vs. asymptomatic donors from Ghana; no immediately apparent correlation of false 85 positive ELISA results with P. falciparum parasitemia was observed (Appendix Table 3) . 86 Nevertheless, a sound statistical analysis of possible correlations with the donors' health 87 status would require larger subgroups/sample numbers than were available for the current 88 study. 89 In contrast to the four indirect IgG ELISA tests evaluated in this study, the Wantai SARS-90 CoV-2 Ab ELISA, detecting total antibodies employing a sandwich antigen procedure, 91 showed a high specificity when applied to a subset of sera from Ghana, Madagascar, and 92 Nigeria (Appendix Figure 1 ). Further testing with this assay was not possible due to the 93 All rights reserved. No reuse allowed without permission. perpetuity. preprint (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in The copyright holder for this this version posted September 18, 2020. improve/restore test specificity, but this may compromise assay sensitivity. 2) If necessary, 120 combine information from two independent serological tests (employing different antigens 121 All rights reserved. No reuse allowed without permission. perpetuity. preprint (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in The copyright holder for this this version posted September 18, 2020. perpetuity. preprint (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in preprint (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in The copyright holder for this this version posted September 18, 2020. . https://doi.org/10.1101/2020.09.15.20159749 doi: medRxiv preprint Figure 1 A B All rights reserved. No reuse allowed without permission. perpetuity. preprint (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in The copyright holder for this this version posted September 18, 2020. . https://doi.org/10.1101/2020.09.15.20159749 doi: medRxiv preprint perpetuity. preprint (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in The copyright holder for this this version posted September 18, 2020. . https://doi.org/10.1101/2020.09.15.20159749 doi: medRxiv preprint WHO, COVID situation report 209 /serology/Serology-based-tests-for-COVID-19.html, as accessed on An evaluation of COVID-19 serological assays informs future diagnostics and 160 exposure assessment Comparison of 162 four new commercial serologic assays for determination of SARS-CoV-2 IgG Performance characteristics of four high-165 throughput immunoassays for detection of IgG antibodies against SARS-CoV-2. 166 Quantification of SARS-CoV-2 antibodies with eight commercially available 169 immunoassays Clinical evaluation of five different automated SARS-CoV-2 serology assays in a cohort of hospitalized COVID-19 patients Responses in the Development of Malaria Infection All rights reserved. No reuse allowed without permission. perpetuity. preprint (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in The copyright holder for this this version posted September 18, 2020. 199 All rights reserved. No reuse allowed without permission.perpetuity.preprint (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint inThe copyright holder for this this version posted September 18, 2020. perpetuity. preprint (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in The copyright holder for this this version posted September 18, 2020. . https://doi.org/10.1101/2020.09.15.20159749 doi: medRxiv preprint