Evaluation of alternative RNA extraction methods for detection of SARS-CoV-2 in nasopharyngeal samples using the recommended CDC primer-probe set

Perez, Vinícius Pietta; Pessoa, Wallace Felipe Blohen; Galvão, Bruno Henrique Andrade; Sousa, Eduardo Sergio Soares; Dejani, Naiara Naiana; Campana, Eloiza Helena; Cavalcanti, Marilia Gabriela dos Santos; Cantarelli, Vlademir Vicente

BACKGROUND The efficiency of isolation and purification of the viral genome is a critical step to the accuracy and reliability of RT-qPCR to detect SARS-CoV-2. However, COVID-19 testing laboratories were overwhelmed by a surge in diagnostic demand that affected supply chains especially in low and middle-income facilities. OBJECTIVES: Thus, this study compares the performance of alternative methods to extraction and purification of viral RNA in samples of patients diagnosed with COVID-19. STUDY DESIGN Nasopharyngeal swabs were submitted to three in-house protocols and three commercial methods; viral genome was detected using the primer-probe (N1 and N2) described by CDC and viral load of samples were determined. RESULTS The in-house protocols resulted in detection of virus in 82.4 to 86.3% of samples and commercial methods in 94.1 to 98%. The disagreement results were observed in samples with low viral load or below the estimated limit of detection of RT-qPCR. CONCLUSION: The simplified methods proposed might be less reliable for patients with low viral load and alternative commercial methods showed comparable performance.