Can a field molecular diagnosis be accurate? A performance evaluation of colorimetric RT-LAMP for the detection of SARS-CoV-2 in a hospital setting

Silva, Lívia do Carmo; Dos Santos, Carlos Abelardo; Mendes, Geovana de Melo; Oliveira, Kézia Gomes de; de Souza Júnior, Marcio Neres; Estrela, Paulo Felipe Neves; Costa, Sérgio Henrique Nascente; Silveira-Lacerda, Elisângela de Paula; Duarte, Gabriela Rodrigues Mendes

SARS-CoV-2 currently represents a serious global public health problem. Non-pharmaceutical intervention measures (NPIs) have been widely adopted, and the testing strategy since the beginning of the infection is the most effective tool for tracking, isolating, and minimizing transmission. The high operating costs and the need for sophisticated instrumentation related to gold standard diagnostic for COVID-19, Reverse Transcription quantitative Polymerase Chain Reaction (RT-qPCR), have highlighted the urgency and importance of developing and applying new diagnostic techniques, especially in places with scarce resources. Thus, alternative molecular tests, such as Reverse Transcription Loop-Mediated Isothermal Amplification (RT-LAMP), based on isothermal amplification have been used to detect SARS-CoV-2 using different protocols. The potential for field application of RT-LAMP is due to the lower cost and time and not requiring high-cost instrumentation. Here, we evaluate the colorimetric RT-LAMP to detect SARS-CoV-2 in a hospital environment and correlate its performance with tests performed in a reference laboratory. The analysis performed at the hospital showed high sensitivity (88.89%), specificity (98.55%), accuracy (95.83%), and a Cohen's kappa of 0.895. However, we achieved 100% of agreement when comparing the RT-LAMP results with the gold standard (qRT-PCR) results for samples with Ct < 30 in the hospital-based test. In addition, a similar performance was found in the field compared to the reference laboratory, corroborating the proposal to apply the test directly at point-of-care.