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.