Estimation of COVID-19 cases in Mexico accounting for SARS-CoV-2 RT-PCR false negative results

Underestimation of the number of cases during the COVID-19 pandemic has been a constant concern worldwide. Case confirmation is based on identification of SARS-CoV-2 RNA using real time polymerase chain reaction (RT-PCR) in clinical samples. However, these tests have suboptimal sensitivity, especially during the early and late course of infection. Using open data, we estimated that among 1 343 730 people tested in Mexico since February 27 ^th , there were 838 377 (95% CL 734 605 – 1 057 164) cases, compared with 604 376 considering only positive tests. ICU admissions and deaths were around 16% and 9% higher than reported. Thus, we show that accounting for the sensitivity of SARS-Cov-2 RT-PCR diagnostic tests is a simple way to improve estimations for the true number of COVID-19 cases in tested people, particularly in high-prevalence populations. This could aid to better inform public health measures and reopening policies.