Figure 3.
Sensitivity evaluation of the RT-LAMP using intact viral RNA of SARS-CoV-2. RT-LAMP was performed using RNA extracts from cell propagated viruses isolated from two patients diagnosed with COVID-19. Intact viral RNA extracts were ten-fold serially diluted (10−2 to 10−9) and processed for detection of SARS-CoV-2. RT-LAMP positive reaction results for each virus isolate 1 (A) and isolate 2 (B) were further confirmed through qRT-PCR (C and D). Limit of detection was assessed using 10−6, 10–7 and 10–8 dilutions in ten repetitions, carried out at 65°C for 30 and 60 min incubation (E and D). Change of colour from phenol red to yellow indicates a positive reaction. RT-LAMP products were electrophoresed at 2 % agarose gel for both RNAs. The ladder-like pattern indicates positive nucleic acid amplification. Cycle threshold (Ct) values were also indicated in each figure as a result of the qRT-PCR.; Lane M: 100 bp DNA ladder; N.D: No detection. *: Limit of detection of qRT-PCR was evaluated using ten repeats of 10−7, 10–8 and 10–9 diluted RNA and the results are shown in Supplementary Table 4.