Testing for the respiratory illness coronavirus disease 2019 (COVID-19) and the associated SARS-CoV-2 virus is possible with two main methods: molecular recognition and serology testing. Molecular methods leverage polymerase chain reaction (PCR) along with nucleic acid tests, and other advanced analytical techniques, to detect the genetic material of the virus using real-time reverse transcription polymerase chain reaction for diagnostic purposes.
Serology testing, leverages ELISA antibody test kits to detect the presence of antibodies produced by the host immune system against the virus. Typically two ELISA tests against two different proteins produced by the virus on between 2 and 4 samples taken from sputum and swabs taken nasally and from the mouth. If either test is positive, a microneutralization assay test is performed to confirm the positive result.
The microneutralization assay is highly specific, but significantly more labor and time intensive. Since antibodies continue to circulate even after the infection is cleared, serology tests continue to be positive for individuals who have been previously exposed and developed an immune response, which means a positive test may not indicate an active infection. Serology antibody testing is being used both for surveillance and investigational purposes including, in China, confirmation of recovery, only while the molecular test methodologies are used to diagnosis active infections.
Chest CT scans can sometimes help identify and characterize lung pathology, and have yielded non-specific findings with COVID-19 infection. A systematic review of chest CT scan findings in 919 patients described the typical early manifestation of COVID-19 as “bilateral multilobar ground-glass opacification (GGO) with a peripheral or posterior distribution”. One study found that the sensitivity of CT for COVID-19 infection was 98% compared to RT-PCR sensitivity of 71%; however, this was performed in Wuhan province of China and is not generalizable.