Table 3.

A comparison of different SARS-CoV-2 detection methods.

Methods	Principle/ target of detection	Limit of detection	Time (h)	Merits	•Demerits	Ref
RT-PCR	RNA template converted into cDNA which is amplified. Specific primer-probe based detection of viral RNA	95%; 100 copies of RNA per ml of transport media (approx.)	3–4 h	•high sensitivity and specificity •thousand of samples analyzed in one day •detection of early and lo viral titers	•false positive results due to cross-reactivity of primers with nucleic acids (in case of other infections) •false negative results due to mutations in primers and probe of the genome of SARS-CoV-2	[16,21]
RT-LAMP	Based on autocycling strand displacement DNA synthesis. Uses more than two sets of specific primer for detection.	a copy of the RNA template per reaction	60–90 min	•high sensitivity and specificity •least turnaround time •no need of thermal cycler	•requires expensive infrastructure, skilled personnel •difficulty in sample transportation	[22]
NP antigen detection test	Viral antigen (nucleocapsid protein) detection. Point-of-care (PoC) test.	0.58 copies per μl	15–30 min	•no requirement of equipped lab •easy analytical method	•low sensitivity •no real studies performed	[66]
Plasmonic biosensor	Use label free probe of biological analytes for detecting molecules (viral particles) at much lower concentration	0.22 pM of viral particles	Few minutes	•high detection with low concentration, fast detection	•error can occur due to non-specific binding on SPR disc •steric hindrance due to immobilization of bioreceptors	[41]
Bioelectric biosensor	Uses biorecognition element that reacts with target and produce signal proportional to the concentration of the target.	1 fg/ml	3 min	•requires less duration to detect •high specificity •no requirement of prior sample processing	•reduction in cell viability may affect the detection	[44]
Microarray based techniques	The target DNA fragments with fluorescent probes bind with probes of DNA chip due to complementarity which is measured using fluorescence emission.	100%	10 min	•high throughput technique •efficient detection method •fast detection	•high cost due to use of fluorescent oligonucleotides	[13,50]
ELISA	Antibody detection using a specific antigen (enzyme substrate reaction).	97.8% IgG	4–6 h	•less expensive, medium turnaround time •data confirmation by meta-analysis and cohort data •easy collection of sample	•fails to detect early stage of infection as IgG/ IgM did not appear •cannot detect patients with mild infections	[21,54]
NGS based platform	Whole genome sequencing	100%	1–2 day	•high accuracy •genomic profiling of virus is done	•very expensive •better for genetic mapping than diagnosis	[55,56]
CRISPR-Cas-based detection	Finds a specific bit of DNA inside a cell.	10 copies per microlitre of viral RNA	40–60 min	detection within minutes, low cost	•requires validation	[59,61,62]
Digital platforms for detection/ tracking	By recording Cough or speech pattern or other physiological manifestations and applying AI	Can be detected symptomatic/ asymptomatic patients accurately	Few minutes	Yet not implemented in larger set up	•Very accurate	[[63], [64], [65]]