The best method is nucleic acid amplification based test. In case of SARS-CoV2 it is the Real Time RT-PCR, which is widely being used globally. In the coming days other non-PCR based nucleic acid amplification tests may be used.
WHO has listed the first two diagnostic tests for emergency use during the Covid-19 pandemic. The move should help increase access to quality-assured, accurate tests for the disease. It also means that the tests can now be supplied by the United Nations and other procurement agencies supporting the COVID-19 response.