Abstract
Estimate the detection limits of the COVID-19 surveillance system (SS) in Chile, by estimating the SARS-CoV-2 true prevalence (TP) and the reported official positivity prevalence (OPP) gap. Randomized cross-sectional. Two sampling campaigns (SC) were conducted (October-November 2020 and December 2020-January 2021) in the cities of Temuco, Valdivia, and Osorno. Blood was collected from adults from randomly selected households. Sera were analyzed using a commercial later flow test (LFT). A meta-analysis was performed to estimate LFT-performance in asymptomatic-cases. Data were analyzed using a Bayesian latent class model (BLCM) to estimate TP. Finally, BLCM outputs were compared with the OPP, by calculating the TP/OPP rate. 1124 and 1017 households were visited during the 1st and 2nd SC, respectively. The BLCM rendered TP estimates of 6.5%, 3.2%, and 6.6% for the cities of Temuco, Valdivia, and Osorno, respectively (1stSC), increasing to 9.4%, 5.0%, and 7.5%, 60 days later (2ndSC). Depending on the city and SC, TP/OPP rates varied between 2.3 and 5.7. The national SS was unable to detect 70-79% of all infected cases, suggesting that mild and asymptomatic cases were scarcely detected.
Published Version
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