Rapid antigen tests for large-scale diagnostic campaigns: A case study from North-Eastern Italy
Authors: Matteo Riccò, Silvia Ranzieri, Federico Marchesi
Journal: Journal of Infection (2021)

As pointed out by Alemany et al. in their recent report "Analytical and clinical performance of the panbio COVID-19 antigen detecting rapid diagnostic test", rapid antigen diagnostic (RAD) tests may be instrumental for scaling up our diagnostic capacity.1Alemany A Baró A Ouchi D Ubals M Corbacho-Monné M Vergara-Alert J et al.Analytical and clinical performance of the PANBIO Covid-19 antigen-detecting rapid diagnostic test.J Infect. 2021; (S0163-4453(21)00004-9)https://doi.org/10.1016/j.jinf.2020.12.033Abstract Full Text Full Text PDF PubMed Scopus (56) Google Scholar,2Cerutti F Burdino E Milia GM Allice T Gregori G Bruzzone B et al.Urgent need of rapid tests for SARS CoV-2 antigen detection: evaluation of the SD-biosensor antigen test for SARS-CoV-2.J Clin Virol. 2020; 132104654https://doi.org/10.1016/j.jvc.2020.104654Crossref PubMed Scopus (0) Google Scholar Unfortunately, some field reports suggest that their real-world sensitivity may not exceed 70%, eliciting some concerns on their use for large-scale testing campaigns.3Lambert-Niclot S Cuffel A Le Pape S Vauloup-Fellous C Morand-Joubert L Roque-Afonso AM et al.Evaluation of a rapid diagnostic assay for detection of SARS-CoV-2 antigen in nasopharyngeal swabs sidonie.J Clin Microbiol. 2020; 58 (20): e00977PubMed Google Scholar In this regard, a mass-scale testing campaign was performed by means of RAD tests in the Italian province of South Tyrol, and respective open data have been made available by local authorities, allowing their third-party analysis.4Presidenza del Consiglio dei Ministri – Dipartimento della Protezione Civile – Roma – COVID-19 Italia Monitoraggio della situazione - 2020-2021 available from: https://github.com/pcm-dpc/COVID-19 [accessed on: January 15th, 2021].Google Scholar,5Bundesministerium für digitalisierung und wirtschaftsstandort – österreichisches COVID-19 open data informationsportal, available from: https://www.data.gv.at/covid-19/ [accessed on: January 15th, 2021]Google Scholar For instance, during November 2020, Italian province of South Tyrol experienced a surge of daily notification rates for SARS-CoV-2 cases (i.e. 7-days moving average of 103.4/100,000 inhabitants, 95%CI 95.4–111.4 for the time period 1/11/2020 to 20/11/2020), that substantially doubled those of the bordering Italian region of Trentino (i.e. 42.8/100,000 inhabitants, 95%CI 42.8–44.6), and the Austrian State of Tyrol (i.e. 40.1/100,000 inhabitants, 95%CI 38.0–42.2). Trentino, Tyrol and South Tyrol are of similar size, comparable populations density, sharing significant cultural and environmental features. However, during the ongoing SARS-CoV-2 pandemic, such areas have been characterized by heterogenous approaches to the public health measures, both in terms of actual interventions and their timing. In order to cope with frightening notification rates, local authorities from South Tyrol implemented a voluntary large-scale screening campaign based on RAD tests for SARS-CoV-2, that in 3 days (20/11/2020–22/11/2020) involved a total of 361,781 people (67.9% of the total population).6Local health authority of bolzano south tyrol – screening a livello provinciale per il contenimento del coronavirus available from https://coronatest.sabes.it/it/muni [accessed on: January 15th, 2021]Google Scholar As shown in Fig. 1, 7-days average of daily notification rates dropped from 110.9 (20/11/2020) to 31.5 cases/100,000 inhabitants (23/12/2020), being afterwards comparable to those of Trentino (in average: 34.5/100,000, 95%CI 32.0–36.9 for South Tyrol, vs. 35.0 95%CI 33.1–37.0, for Trentino), but still higher than those of Tyrol (10.5/100,000 inhabitants, 95%CI 9.7–11.2), seemly suggesting the substantial efficacy of this intervention. However, after daily rates were percent normalized to their respective maximum values in order to cope with the different diagnostic strategies, epidemic curves of the three regions substantially overlapped until the end of December 2020, as sharing a common trend (Fig. 2). More precisely, normalized rates were similar in the 14 days following the mass screening test in South Tyrol (i.e. 78.9%, 95%CI 73.2–84.7 for South Tyrol; 81.5%, 95%CI 77.7–85.2 for Trentino; 76.6%, 95%CI 71.2–82.0 for Tyrol, ANOVA p value = 0.285), and they remained well correlated across all the assessed timeframe (i.e. r = 0.818, p < 0.001 for South-Tyrol vs. Trentino, and 0.973, p < 0.001 for South Tyrol vs. Tyrol). In summary, available estimates cannot confirm the unambiguous effect of the large-scale screening intervention on the circulation of SARS-CoV-2 in South Tyrol, eventually urging for a more cautious implementation of RAD tests for SARS-CoV-2 in mass scale testing7European Centre for Diseases Prevention and Control (ECDC). An overview of the rapid test situation for COVID-19 diagnosis in the EU/EEA. Stockholm, 2020.Google Scholar. We declare no competing interest. The facts, conclusions, and opinions stated in the article represent the Authors' research, conclusions, and opinions, and are believed to be substantatiated, accurate, valid, and reliable. However, as this article includes the results of personal researches of the Authors, presenting correspondent, personal conclusions, and opinions, parent employers are not forced in any way to endorse or share its contents and its potential implications.