EPICOVID19: Psychometric assessment and validation of a short diagnostic scale for a rapid Covid-19 screening based on reported symptoms (Preprint)

BACKGROUND: Coronavirus disease (COVID-19) confirmed cases have been registered in more than two hundred countries and, of July 28, over 16 million cases have been reported to WHO. The present study was conducted while the epidemic peak of COVID-19 was occurring in Italy. The early recognition is critical for the identification of suspected cases to be immediately subjected to quarantine. Although surveys are widely used for identifying COVID-19 cases, outcomes and associated risks, no validated epidemiological tool exists for surveying (SARS-CoV-2) infection in the population so far. OBJECTIVE: We evaluated the capability of self-reported symptoms to discriminate the COVID-19, in order to identify possible cases to undergo instrumental measurements. We defined and validated a method for the identification of a cut-off score. METHODS: Our study is the phase II of the EPICOVID19 Italian national survey, launched in April 2020 including a convenience sample of 201121 adults, who filled the EPICOVID19 questionnaire. The Phase II questionnaire, focused on results for nasopharyngeal swab (NPS) and/or serological tests, was mailed to all subjects who previously underwent NPS tests. RESULTS: Of 2703 subjects who completed the Phase II questionnaire, 694 (25.7%) were NPS(+). In the individuals who performed serological testing, of the 472 who did Immunoglobulin-G (IgG) test and 421 who did Immunoglobulin-M (IgM) test, 22.9% (108 out of 472) and 11.6% (49 out of 421) tested positive, respectively. Compared with NPS(-), among NPS(+) subjects there was a higher rate for Fever (421 [60.7%] vs 391[19.5% ]; P =60 years group the cut-off score was 1.28 and the accuracy detected by Antibodies IgG(+) was improved (Se 88.00; Sp 89.58). CONCLUSIONS: We developed a short diagnostic scale to detect subjects with symptoms potentially associated with COVID-19 among a wide population, which supports the potential for identifying individuals who need to seek immediate clinical evaluation. Although these results are referred to the Italian pandemic period, this short diagnostic scale could be optimised and tested as a screening tool in other similar pandemic contexts.