Abstract
The use of RT-LAMP (reverse transcriptase—loop mediated isothermal amplification) has been considered as a promising point-of-care method to diagnose COVID-19. In this manuscript we show that the RT-LAMP reaction has a sensitivity of only 200 RNA virus copies, with a color change from pink to yellow occurring in 100% of the 62 clinical samples tested positive by RT-qPCR. We also demonstrated that this reaction is 100% specific for SARS-CoV-2 after testing 57 clinical samples infected with dozens of different respiratory viruses and 74 individuals without any viral infection. Although the majority of manuscripts recently published using this technique describe only the presence of two-color states (pink = negative and yellow = positive), we verified by naked-eye and absorbance measurements that there is an evident third color cluster (orange), in general related to positive samples with low viral loads, but which cannot be defined as positive or negative by the naked eye. Orange colors should be repeated or tested by RT-qPCR to avoid a false diagnostic. RT-LAMP is therefore very reliable for samples with a RT-qPCR Ct < 30 being as sensitive and specific as a RT-qPCR test. All reactions were performed in 30 min at 65 °C. The use of reaction time longer than 30 min is also not recommended since nonspecific amplifications may cause false positives.
Highlights
The use of Reverse transcription loop-mediated isothermal amplification (RT-LAMP) has been considered as a promising point-of-care method to diagnose COVID-19
Approaches to detect SARS-CoV-2 based on RT-LAMP have been used broadly as an alternative point-of-care test to detect this disease, including the testing of clinical samples[13,14], with reaction time varying between 15 and 40 minutes
Lamb et al[18] designed highly specific primers based on the GenBank MN908947 sequence and successfully detected 27 strains of COVID-19 from various locations, which presented no cross reaction with three non-SARS-CoV-2 viruses
Summary
The use of RT-LAMP (reverse transcriptase—loop mediated isothermal amplification) has been considered as a promising point-of-care method to diagnose COVID-19. In this manuscript we show that the RT-LAMP reaction has a sensitivity of only 200 RNA virus copies, with a color change from pink to yellow occurring in 100% of the 62 clinical samples tested positive by RT-qPCR. The performance of these tests has not been ideal In one of these m ethods[15], for example, a sample of water was used as a negative control instead of human RNA, which could have led to a false negative result. We discuss the presence of a third color cluster never described before that could lead to a wrong diagnosis
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
