Population Medicine (Oct 2020)
Effectiveness of COVID-19 case definition in identifying SARS-CoV-2 infection in northern Mexico
Abstract
Introduction In Mexico, a new COVID-19 case definition was released on 24 March 2020, this definition is no different from the one used for epidemiological surveillance of influenza-like illness since 2009. We aim to evaluate the effectiveness of the COVID-19 suspected case definition in identifying SARS-CoV-2 infection in Tijuana, a US-border city in Mexico. Methods A cross-sectional database study was conducted, including entries from 11 March to 1 May 2020. COVID-19 case definition was compared to RT-PCR results using 2×2 tables to estimate sensitivity, specificity, PPV, NPV, accuracy and likelihood ratios (LR). Categorical variables were analyzed using χ 2 test. Stratification by gender, age group, history of chronic disease and severity of presentation was performed to control for confounding. Results From a total of 10216 entries, 897 patients with results from RT-CPR for SARS-CoV-2 were included. There was no significant association between COVID-19 case definition and RT-PCR result (χ 2 =0.750, df=1, p=0.386). A sensitivity of 87.45%, specificity of 10.61%, PPV of 61.69%, and NPV of 33.96% were calculated, with an overall accuracy of 58.42%, LR+ was 0.98 and LR- was 1.18. Stratifying by age, homogeneity of OR=0.024 showed an association between case definition and test result particularly among those aged 16-39 years (p=0.014). Only 4 individual symptoms had a statistical association with RT-PCR result. These were dyspnea (p<0.001), odynophagia (p<0.001), rhinorrhea (p<0.001) and fever (p=0.008). Conclusions Satisfying criteria for COVID-19 case definition neither showed a significant association nor is it a powerful predictor for SARS-CoV-2 infection among the study population. However, this COVID-19 case definition better identifies those cases in those aged 16-39 years, suggesting a possible relation between the type of the clinical presentation and age.
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