Flocked swab might be one main reason causing the high false-negative rate in COVID-19 screening----the advantages of a novel silicone swab

Zhou, Jianye; Bai, Zhongtian; Jiang, Nan; Li, Xiaodong; Zhang, Xiaohui; Li, Zhiqiang; Li, Yonghong; Ma, Zhongren; Zhao, Jin

RNA testing using RT-PCR can provide direct evidence for diagnoses of COVID-19 which has brought unexpected disasters and changes to our human society. However, the absorption of cotton swab for RNA lysates may lead to a low concentration of detectable RNA, which might be one of the main reasons for the unstable positive detecting rate. We designed and manufactured a kind of silicone swab with concave-convex structure, and further compared the effects of silicone and cotton swab on RNA extraction. Principal component analysis and Paired Wilcoxcon test suggested that a higher RNA concentration and A260/A280 would be obtained using silicone swab. The results indicated that our silicone swab had a more excellent ability to sample than the cotton swab, characterized by the higher quantity and quality of extracted RNA. Thus, we advised that the current cotton swabs need to be improved urgently in COVID-19 diagnoses and the process of "sample collection" and "sample pre-processing" must be standardized and emphasized. HighlightsThe current cotton swabs need to be improved urgently in COVID-19 screening.