The novel coronavirus, SARS-CoV-2, causes the Coronavirus disease-2019 (COVID-19) and this pandemic. It is highly infective, and everyday thousands of people are newly infected. Since there is no vaccine or cure for the novel coronavirus infection till today, there is a strong need for rapid, specific and sensitive SARS-CoV-2 detection technology to control and contain the virus.
The current method for SARS-CoV-2 diagnosis is the real time reverse transcription polymerase chain reaction (RT-PCR) test which detects the presence of viral nucleic acids in nasopharyngeal swab samples. But it has certain shortcomings. The test requires complex and costly equipment. It requires extensive training for potential users. As the specificity and sensitivity of the test is about 95%, there is a possibility of false negative results. The turnaround time is about 10 hours, so that the result will be available only by the next day. In remote places, the turnaround time further increases depending on the distance the samples need to travel. In short, the RT-PCR does not have the capacity to keep pace with the increasing demand.
COVID-19 serology tests are also in use to detect antigens that are associated with the virus infection. These tests are easy to use with rapid results, as well as have minimal expenses. However, serology immunoassay lacks the necessary accuracy to be a reliable diagnostic test due to its low sensitivity and high false negative/positive rates.
With the above-mentioned status of COVID-19 detection ambiguity, there is an urgent need for a better technique for COVID-19 testing. This superior technique is now in India in the form of RT-LAMP (Reverse Transcriptase loop-mediated isothermal amplification) technology. This is a one-step nucleic acid amplification method to multiply specific sequences of RNA of the coronavirus. Here, the RNA is first made into cDNA (copy DNA) by the usual reverse transcription. Then, the DNA is amplified by the LAMP technique. Although the LAMP technique has been used in western countries for the past five years or more, the technique is new to the Indian IVD industry.
The LAMP technology has many advantages over RT-PCR technology. The RT-PCR test needs different temperatures in one cycle. The temperature of the solution has to be changed from 92 degrees C to 56 degrees C and again to 72 degrees C every two minutes, and this cycle has to be repeated. Thus, the PCR test needs expensive thermal cycler as well as the real time PCR machines. On the other hand, the new RT-LAMP technology is done at 65 degrees C, where the DNA amplification is done at a constant temperature (isothermal), so that expensive thermal cycler is not required.
Moreover, the quantity of DNA amplified in the LAMP technology is hundred thousand times more than that is taking place in PCR. Therefore the final assay is possible with a simple colour reaction, removing the need for very costly real time PCR machines.
An equally important advantage of the LAMP technology is that the assay is so fast that results can be obtained within 30 minutes and positive samples are amplified as early as 10 minutes. This may be compared with the PCR technique which needs 8–10 hours for completion. This means that COVID-19 testing centres can report with accuracy in substantially lower turnover time.
Yet another advantage of LAMP is that the reagents are to be stored at 4 degree C (ordinary fridge), whereas the PCR-based reagents are to be stored and transported at –20 degrees C, which needs deep freezers that escalate the cost.
The LAMP technology does not need laborious preparation as in the case of RT-PCR. LAMP is cost effective and does not need complex expensive equipment. Assays can be performed with minimum skill and minimum infrastructure.
The LAMP technology has been recently validated by the Indian Council of Medical Research with sensitivity 98.7% and specificity 100%. Thus the LAMP technology is superior to the PCR technology–based COVID-19 kits where specificity is around 95% only. Thus, in the case of LAMP-based kits, the Positive predictive value is 100% and Negative predictive value is 98.8% with accuracy of 99.38%.
A confirmatory, accurate, rapid, low-cost, and user-friendly molecular diagnostic method is the prerequisite to address COVID-19 pandemic. The RT-LAMP technology is ideal for Indian conditions. There is an urgent need to build the national testing capacity above what is achievable with currently available test kits. This is possible with RT-LAMP technology which shows great promise as a detection tool. The procedure’s speed, simplicity and cost-effectiveness allow it to be the ideal method for diagnosing the infection.
Agappe Diagnostics have recently developed the LAMP technology indigenously, and their kit has been validated and approved by the ICMR for marketing. It is named LUME Screen nCoV
(The writer is Head of postgraduate programmes and research at Amrita Institute of Medical Sciences, Kochi.)