Table 3.

Practical diagnostic considerations of RT-PCR test and Serological immunoassay.

	RT-PCR test	Antibody test
Merit	Highly specific	Easy to use serological sample
Limitation	Sensitivity can suffer due to sampling errors or insufficient viral load (false negatives). Inactive virus and viral fragments could also test positive (false positives).	Generally not as accurate as RT-PCR test, with false positives and false negatives. False positives in a low prevalence population can give an exaggeration of exposure and immunity. (e.g., a specificity of 99% in a population of 1% prevalence can lead to ~50% of positive results being false.)
Remedy	Testing twice sequentially to improve sensitivity (e.g., a single test sensitivity of 70% would result in a 2-test sensitivity of 91%) and/or combination with chest CT scan and clinical factors	Assay validation with sufficient positive and negative sample cohorts; generally cannot be used to diagnose newly infected patients, but can be used as a screening test (Optimizing antibody test sensitivity for rule-out, optimizing specificity for rule-in)
Primary utility	Standard of care diagnosis of newly infected and/or active Covid-19 patients.	Screening test for stratifying newly infected patients, remotely infected patients, and asymptomatic patients; surveillance assay for seroprevalence, immunity and vaccination efficacy.