OmniLAMP® - A portable colorimetric LAMP system for fast and reliable clinical molecular detection of SARS-CoV-2.

Despite the transition of COVID-19 from a global emergency to sustained circulation, SARS-CoV-2 continues to evolve, reinforcing the need for rapid, reliable, and decentralized molecular diagnostic tools. Reverse transcription loop-mediated isothermal amplification (RT-LAMP) represents an alternative to RT-qPCR, particularly for point-of-care (PoC) applications. In this study, we evaluated the OmniLAMP® portable PoC platform for SARS-CoV-2 detection in clinical saliva samples using colorimetric RT-LAMP targeting the SARS-CoV-2 N/E genes, using either extracted RNA or an extraction-free saliva processing protocol based on proteinase K treatment followed by heat inactivation. OmniLAMP® maintained stable isothermal conditions at 65 °C during amplification and incorporated automated image-based interpretation of colorimetric results. Using RT-qPCR as the reference method, RT-LAMP performed with extracted saliva RNA showed high diagnostic performance, with 100% sensitivity and clinical specificity up to Ct ≤ 34 and no statistically significant difference from RT-qPCR even when samples up to Ct ≤ 40 were included (88% sensitivity, 100% specificity; McNemar p = 0.125). Importantly, extraction-free processed saliva also showed high performance in samples with higher viral loads, achieving 90% sensitivity at Ct ≤ 30 and 85% at Ct ≤ 34, with 100% specificity and no statistically significant difference from RT-qPCR up to Ct ≤ 34 (McNemar p = 0.250). Sensitivity decreased to 56% when samples with Ct values up to 40 were included, indicating reduced detection capability at lower viral RNA levels. Overall, the integration of non-invasive saliva collection, simplified extraction-free processing, isothermal amplification, and automated result interpretation supports the potential application of OmniLAMP® for rapid and decentralized molecular testing, particularly in settings where simplicity and reduced dependence on laboratory infrastructure are important.