New Ultrarapid COVID-19 Test Gives Highly Accurate Results Faster than PCR and LAMP Tests

The Birmingham COVID-19 test, called RTF-EXPAR, gives a sample-to-signal time of under 10 minutes, even for low viral levels where current lateral flow tests are less effective.

The study revealed that the RTF-EXPAR method converts under 10 strands of RNA into billions of copies of DNA in under 10 minutes, using a one-pot assay that is compatible with more basic, benchtop equipment than that used with current testing methods. RTF-EXPAR also demonstrated significant improvements over both PCR and LAMP-based assays on time to signal detection. At low concentrations of RNA (7.25 copies/µL), the time to signal detection was 42.67 (± 0.47) minutes for PCR, 11.25 (± 0.20) minutes for LAMP, and 8.75 (± 0.35) minutes for EXPAR. At high (1450 copies/µL) concentrations of viral RNA, the time to signal detection was 34.00 (± 0.00) minutes for PCR, 11.25 (± 0.20) minutes for LAMP, and 3.08 (± 0.42) minutes for EXPAR.

Identification of the optimal sequence was clearly an important step in the development of the EXPAR method, and the sequence detected in the study, which comes from the Orf1ab gene in the SARS-CoV-2 genome, has been shown to be conserved in all current variants of COVID-19. However, the RTF-EXPAR method can be quickly adapted should new variants emerge, or for testing other viral pathogens such as Influenza, Respiratory Syncytial Virus (RSV), or Ebola, where near-patient testing is required to prevent more widespread transmission.

“Both the reverse transcription and amplification steps slow down existing COVID assays that are based on nucleic acid detection, compared to antigen tests, such as lateral flow, which do not have these steps,” said Professor Tim Dafforn from the School of Biosciences. “However, while this makes lateral flow tests faster than those based on PCR and LAMP, in return they are typically less sensitive. An ideal test would be one that is both sufficiently sensitive and speedy – our test, called RTF-EXPAR, achieves this goal.”

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