Determinants of SARS-CoV-2 nasopharyngeal testing in a rural community sample susceptible of first infection: the CHRIS COVID-19 study

Abstract

Background To rapidly characterize COVID–19 epidemiology, numerous population-based studies have been undertaken to model the risk of SARS–CoV–2 infection. Less is known about what may drive the probability to undergo testing. Understanding how much testing is driven by contextual or individual conditions provides the basis for unbiased representation of testing figures and shaping of public health interventions and resource allocation. Methods In the Val Venosta/Vinschgau district (South Tyrol, Italy), we conducted a population-representative longitudinal study on 697 individuals who completed 4,512 repeated online questionnaires at four week intervals between September 2020 and May 2021. Mixed–effects logistic regression models were fitted to investigate associations between self-reported SARS–CoV–2 testing and both individual characteristics (social, demographic, and biological) and contextual determinants. Results Testing was associated with month of reporting, reflecting the timing of both the pandemic intensity and public health interventions, COVID–19–related symptoms (odds ratio, OR:8.26; 95% confidence interval, CI:6.04–11.31), contacts with infected individuals within home (OR:7.47, 95%CI:3.81–14.62) or outside home (OR:9.87, 95%CI:5.78–16.85), and being retired (OR:0.50, 95%CI:0.34–0.73). Within– and outside–home contacts were the leading determinants in the first and second half of the period, respectively, possibly reflecting later relaxation of social–distancing measures. Testing was not associated with age, sex, education, comorbidities, or lifestyle factors. Conclusions In the study area, contextual determinants reflecting the course of the pandemic were predominant compared to individual sociodemographic characteristics in explaining the SARS–CoV–2 probability testing. Decision makers should evaluate whether the intended target groups were correctly prioritized by the testing campaign.

Trends and symptoms of SARS-CoV-2 infection: a longitudinal study on an Alpine population representative sample

“…However, self-reported symptoms have shown greater breadth than electronic medical record-extracted symptoms 49. Moreover, another report on the same cohort21 showed that if participants were to experience symptoms they would generally be tested for COVID-19, limiting the possibility of testing bias in our results.…”

“…We invited an age-sex stratified random sample targeting 1450 participants of the Cooperative Health Research in South Tyrol (CHRIS) study29 representative of all adult residents in the district to participate in the CHRIS COVID-19 prospective investigation between 13 July and 28 August 2020 20 21. An online screening questionnaire covered SARS-CoV-2-related anamnesis since 1 February 2020 until participation to the baseline clinical visit for blood drawing and testing.…”

“…Follow-up questionnaires focused on SARS-CoV-2 anamnesis and additionally included ‘vaccination status’ from the beginning of the vaccination campaign (27 December 2020). At each follow-up, participants replied to a main filter question on SARS-CoV-2-related events since previous participation: on a positive reply, the participant would fill in the rest of the questionnaire, otherwise all subsequent responses were considered negative, or else missing in case of no response 20 21…”

“…While planning, recruiting and accrual of evidence are time consuming, these studies have a unique and active role in shaping surveillance strategies 4. By the end of August 2020, we recruited a representative random sample of adult residents in the Alpine rural district of Vinschgau/Val Venosta (South Tyrol, Italy) 20 21. As few as 4.4 cases per 10 000 district inhabitants and no active cases (16 confirmed cases overall) had been identified by the healthcare system at the time, in contrast to nearby and other European regions, where infection prevalence estimates ranged from 23.1% to 42.4% in the same period 22–24.…”