The Current Status and Challenges in the Development of Vaccines and Drugs against Severe Acute Respiratory Syndrome-Corona Virus-2 (SARS-CoV-2)

Table 1

List of rapid methods used for detecting SARS-CoV-2.

Diagnostic tests	Mechanism	Sample	Advantages	Limitations
Direct tests
RT-PCR	SARS-CoV-2-specific hybridization probes are used to target envelope (E), RNA-dependent RNA polymerase (RdRp), and ORF1b and N regions of the virus. This test can detect the virus at least after two days after infection	Upper respiratory tract (URT) and lower respiratory tract (LRT) specimens	This test is a gold standard method for the diagnosis in symptomatic and asymptomatic patients. This test has a high sensitivity (~89%) and specificity (99%)	Needs infrastructure, very expensive, and requires qualified personnel
Reverse transcription loop-mediated isothermal amplification	Exponential amplification of virus-specific genes at a constant temperature	URT and LRT specimens	High sensitivity and specificity	Needs infrastructure, very expensive, and requires trained personnel
Nucleoprotein (NP) antigen detection test	Enzyme-linked immunoassay has a microplate precoated with specific antibodies against SARS-CoV-2 NP and the use of horseradish peroxidase- (HRP-) labeled secondary antibody	URT and LRT specimens and saliva	Simple and rapid technique. No trained personnel and expensive laboratory instruments are required	Less sensitivity (70-86%) and specificity (95-97%) when compared to RT-PCR
Indirect tests
ELISA	Detects anti-SARS-CoV-2 IgG and IgM by identifying antibodies against the NP and spike proteins	Serum, plasma, whole blood	Widely used technique, inexpensive, easy sample collection, and high sensitivity (~82%) and high specificity (97%)	Needs infrastructure and trained personnel
Chemiluminescent immunoassay	Light-producing chemical reactions estimate the titers of IgG and IgM by the amount of the emitted luminous signal	Serum, plasma, whole blood	High-throughput and sensitive (77.9%) technique	Needs infrastructure and trained personnel
Rapid detection kits	Device with colloidal gold-labeled SARS-CoV-2 recombinant protein and murine anti-human IgG antibodies	Fingerpick blood samples	No need of infrastructure, easy sample collection results in 10-15 min	Low sensitivity (~88.6%) and specificity (~90.63%)

Even though several detection methods have been developed, RT-PCR is considered as the gold standard for detection of SARS-CoV-2. The details presented in the table show various diagnostic approaches that have been developed in the detection of SARS-CoV-2.