COVID-19 symptoms: A case-control study, Portugal, March-April 2020

Abstract

COVID-19, although a respiratory illness, has been clinically associated with non-respiratory symptoms. We conducted a negative case-control study to identify the symptoms associated with SARS-CoV-2 positive results in Portugal. Twelve symptoms and signs included in the clinical notification of COVID-19 were selected as predictors, and dependent variable was the RT-PCR test result. Chi-squared tests were used to compare notified cases on sex, age group, health region and presence of comorbidities. The best fit prediction model was selected using a backward stepwise method with an unconditional logistic regression. General and gastrointestinal symptoms were strongly associated with a positive test (p<0.001). In this sense, inclusion of general symptoms such as myalgia, headache and fatigue, as well as diarrhoea, together with actual clinical criteria for suspected cases, already updated and included in COVID-19 case definition, can lead to an increased identification of cases and represent an effective strength for transmission control.