Skip to main content
[Preprint]. 2020 Aug 18:rs.3.rs-56028. [Version 1] doi: 10.21203/rs.3.rs-56028/v1

Figure 1.

Figure 1

Validation of alternative swabs and storage buffer (95% EtOH and 91% isopropanol) in RNA recovery and detection of COVID-19. a) Human RNAse P gene (Rp) amplification was used to compare nucleic acid extraction efficiency across sample processing methods. Clinical gold-standard synthetic-tipped plastic-shaft NP swabs stored in VTM and extracted from 200 μL of eluent (left, n=39) have significantly higher copy numbers compared to 200 μL EtOH eluent from SYN nares swabs (middle, n=22), but not when extracted from the EtOH-preserved swab head (right, n=18). One-way ANOVA with Tukey’s multiple comparison VTM eluent vs EtOH eluent p=<0.001, EtOH eluent vs EtOH swab p<0.001, VTM vs EtOH swab p = 0.266. b) Extrapolated viral RNA copy number from COVID-19 positive nares samples collected with BD synthetic swabs in the hospital stored in 95% EtOH and extracted from either the eluent or swab from the same sample (n=24, one-tailed paired Student’s T-test p=0.032). c) Proportion of RNA recovered across three storage buffers: None, 95% EtOH, and 91% isopropanol using commercial human RNA added to storage buffers (ns, one-way ANOVA p>0.05). d) Evaluation of RNaseA inhibition by 95% EtOH (grey) and 91% isopropanol (blue) using either the human Rp or SARS-CoV-2 N1 primer set on control RNA added to each solution (unpaired t-tests of 95% EtOH vs 91% Iso per each marker at 0, 2500, 25000 ng RNaseA). e) Comparison human RNA recovery across six swab types (SYN=synthetic rayon ‘commercial’, BDF=BD foam ‘commercial’, TMI=BD TMI ‘commercial’, CGp=plastic ‘consumer-grade’, Pu=Puritan ‘commercial’, CGw=wood ‘consumer-grade’), extracted from 200μL eluent (blank bar) or the swab head. Recovery for each swab type is normalized to the CDC recommended method (eluent from PE swab). A ‘2’ would indicate there was 2x more RNA recovered whereas a 0.5 would indicate a 50% reduction in RNA recovery. f) Total RNA copies per extraction for all samples which are grouped by sample-type (eluent or swab head) and storage buffer (95% EtOH or 91% isopropanol). Pairwise comparisons performed within sample-type (not significant) and across sample-type controlling for storage buffer (Mann-Whitney, U=test statistic).