Table 2.

Comparison of diagnosis methods of influenza and COVID-19.

Diagnosis methods	Advantages	Disadvantages	Ref
Influenza	Rapid influenza diagnostic tests (RIDTs)	•Quick outcomes in <15 min •Simple to perform •Available for office/bedside use •RIDTs with CLIA waived can be utilized in settings that include point-of-care •High specificity	•Sub-optimal test sensitivity, false-negative results are common •Influenza B antigens detection sensitivity is lower compared with influenza A antigens •false-positive results •All RIDTs could not discriminate between influenza A or B viruses •Do not give information about influenza A virus or specific virus strain •RIDTs are not able to differentiate between novel influenza A virus and seasonal influenza A infections	[[171], [172], [173]]
	Rapid molecular assay and RT-PCR	•Quick outcomes in approximately 15–30 min to less than 1.5 h •High sensitivity and specificity •Low false positive or false negative result •Some molecular assays can differentiate between specific influenza A virus subtypes •RT-PCR results could be obtained between 4 and 8 h	•Results of some RT-PCR and other molecular assays may not be available in a clinically relevant time frame to inform clinical management decisions •Low availability of RT-PCR facilities •Respiratory specimens may need to be sent to a state public health laboratory or commercial laboratory for RT-PCR •Although the test time is low, the actual time to receive results may be substantially longer •Most FDA-cleared molecular assays are not approved to test lower respiratory tract specimens •High costs of the tests •All molecular assays may not specifically identify all currently circulating influenza A virus subtypes •Problem with the assessment of the accuracy of all available RT-PCR and molecular assays •Rapid molecular assays have lower sensitivity than RT-PCR
	Immunofluorescence (DFA and IFA)	•Antigen detection assays •Outcomes in approximately 2–4 h •High specificity •Both direct (DFA) and indirect fluorescent antibody (IFA) staining assays are available to detect influenza A and B viral antigens in respiratory tract specimens •Can be used as an RIDT with an analyzer device to produce results in approximately 15 min	•A fluorescent microscope is required •Moderate sensitivity •Subtyping or further identification of influenza A virus is not possible by immunofluorescence assays.
	Serologic (antibody detection)	•Antibody assessments may be used in conjunction with viral detection tests to support the clinical assessment of persons who present late in their illnesses •High availability compared with molecular tests •Low costs	•The FDA has not authorized antibody testing to diagnose influenza •The CDC does not currently recommend using antibody testing for the diagnosis of any infection
COVID-19	Real-time PCR	•Authorized assays for viral testing include those that detect COVID-19 nucleic acid or antigen •Viral (nucleic acid or antigen) tests check samples from the respiratory system (such as nasal or oral swabs) or saliva to determine whether COVID-19 is present •High sensitivity and specificity •Low false positive or false negative result •RT-PCR results could be obtained between 4 and 8 h	•Results of some RT-PCR and other molecular assays may not be available in a clinically relevant time frame to inform clinical management decisions •Low availability of RT-PCR facilities •Respiratory specimens may need to be sent to a state public health laboratory or commercial laboratory for RT-PCR •Although the test time is low, the actual time to receive results may be substantially longer •Most FDA-cleared molecular assays are not approved to test lower respiratory tract specimens •High costs of the tests •Problem with the assessment of the accuracy of all available RT-PCR and molecular assays	[83,174]
	Serologic (antibody detection)	•Antibody assessments may be used in conjunction with viral detection tests to support the clinical assessment of persons who present late in their illnesses •High availability compared with molecular tests •Low costs	•The FDA has not authorized antibody testing to diagnose influenza •The CDC does not currently recommend using antibody testing for the diagnosis of any infection