The normal body temperature is about 37°C
Given that I'm not sure about the practices in your country, in normal practice, we followed the CDC guidelines/algorithm for COVID-Testing. I enjoyed the presentation on this website.
https://www.health.harvard.edu/diseases-and-conditions/covid-19-basics
COVID-19 is a respiratory infection, and while it does cause a fever, a fever is not the only symptom of the disease.
The right practice would be to find the cause of the fever and exclude other suspicious causes.
If a respiratory infection seems suspicious, then an antigen test can be done.
I hope this helped address your concern?