New method of visual detection of SARS-CoV-2 can identify the infection at early stage

Context: New method of visual detection of SARS-CoV-2 can identify the infection at an early stage. A new sandwich-based lateral flow immunoassay (LFIA) for the detection of the Receptor Binding Domain (RBD) of severe acute respiratory syndrome-coronavirus-2(SARS-CoV-2) could provide an efficient substitute for RT-PCR tests.

Need for Rapid and Affordable Covid-19 Testing

  • RT-PCR tests are time-consuming and require skilled labour and equipment. Not feasible for large-scale on-site testing.
  • New test kits are needed that are rapid, robust, affordable and can be used for mass testing without skilled personnel. Helps reduce spread by early detection.

Development of Lateral Flow Immunoassay (LFIA) test

  • Scientists from DBT-NIAB and Gandhi Medical College developed an LFIA test for early on-field detection of SARS-CoV-2. Based on antigen-antibody interaction, doesn’t need skilled staff.
  • With DST-SERB support, scientists cloned a gene for SARS-CoV-2 RBD protein, purified and generated antibodies (Ab) against it. AuNPs-Ab is used as a capture probe for colorimetric detection.
  • LFIA test works on sandwich format – RBD antigen in sample interacts with AuNPs-Ab to form complex, moves along the membrane and reacts with RBD Ab coated as test line, giving red colour. The control line verifies test functionality.
  • Different parameters like blocking buffer, and antibody concentration optimized for maximum efficiency. Band intensity was analyzed using a smartphone app for image acquisition/analysis, giving RGB data and intensity trends.

Utility and Cost-Effectiveness

  • LFIA strips are useful as a portable, point-of-care device for on-site SARS-CoV-2 testing at home or in rural areas. Much cheaper than RT-PCR, benefits the economically disadvantaged.
  • Mass production of kits can enable large-scale testing. But quality checks and safeguards are needed to ensure accuracy before policy implementation.
  • If proven highly accurate, LFIA and similar cheap, rapid test kits can revolutionize Covid-19 control strategies in resource-poor settings through early detection and isolation. Can aid in return to normalcy in some activities.

Limitations and Future Prospects

  • Smartphone image analysis provides qualitative, not quantitative results. So not replace RT-PCR’s high accuracy in diagnosis, prognosis and treatment monitoring.
  • As mutations emerge, new generations of test kits may be needed to detect them. Continuous R&D is required to keep up with an evolving virus.
  • Sample size and real-world data on test performance are needed to determine suitability. Regulatory approvals are required before mass uptake.
  • Future prospects: Integrating multiplex detection in one assay; developing rapid confirmatory tests; commercial partnerships for scaling up production at low cost while ensuring quality.

The development of a cheap, rapid lateral flow immunoassay test for SARS-CoV-2 detection is promising for controlling the Covid-19 pandemic through affordable mass testing. However, the test may have limitations in the accuracy and detection of new variants that emerge. Continuous research and policy interventions are needed to enable early, widespread use of fast, low-cost but reliable diagnostics, especially in resource-poor regions bearing high caseloads. New tests that balance speed, cost, accuracy and adaptability will be key to managing coronavirus disease into the future.   

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