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. 2020 May 26;58(6):e00590-20. doi: 10.1128/JCM.00590-20

TABLE 1.

Cycle threshold values for LDT and cobas SARS-CoV-2 assays for nasopharyngeal samples stored in four mediaa

Medium Storage temp (°C) LDT CT value
 cobas SARS-CoV-2 CT value
Day 0
 Day 1
 Day 3
 Day 7
 Day 0
 Day 1
 Day 3
 Day 7
NUC ORF NUC ORF NUC ORF NUC ORF ORF1a E ORF1a E ORF1a E ORF1a E
M4 2−8 29.3 28.3 28.8 28.1 28.6 28.0 28.8 28.1 26.24 27.00 26.43 27.20 26.65 27.29 26.85 27.50
29.6 28.6 29.0 28.2 28.9 28.2 29.6 28.7 25.92 26.84 26.37 27.31 26.66 27.47 27.01 27.80
29.3 28.3 28.6 27.8 28.2 27.2 29.0 28.2 25.99 26.81 26.23 26.9 26.54 27.16 26.83 27.47
−20 29.2 28.2 29.0 28.1 28.9 28.2 29.0 28.4 26.92 27.62 26.65 27.37 26.79 27.43 26.99 27.93
28.8 27.5 29.2 28.4 27.7 27.7 29.2 28.3 26.16 27.05 26.58 27.24 26.87 27.45 26.78 27.44
30.2 28.8 30.7 29.0 29.2 29.2 29.8 28.9 25.72 26.58 26.70 27.43 26.71 27.19 26.96 27.65
MEM 2−8 29.3 28.5 29.0 28.5 28.8 28.4 29.3 28.9 26.55 27.50 26.81 27.73 26.92 27.78 26.92 28.01
28.9 28.1 28.6 28.2 28.4 28.1 28.6 27.9 26.00 26.83 26.89 27.76 27.22 28.02 27.27 28.04
28.8 28.2 28.6 28.4 28.4 28.2 28.4 27.9 26.44 27.33 26.93 27.88 26.70 27.58 27.25 28.13
−20 30.1 28.7 29.8 28.6 29.6 28.6 29.7 28.7 26.49 27.33 26.70 27.76 27.29 28.15 27.53 28.31
29.7 28.0 29.2 28.4 27.8 26.5 29.4 28.6 26.54 27.59 26.99 27.99 27.35 28.21 27.58 28.50
28.6 27.7 28.5 28.2 28.6 28.6 29.6 29.0 26.79 27.63 27.09 27.99 27.34 28.10 27.53 28.47
PBS 2−8 30.1 28.7 29.0 27.8 29.7 28.7 29.7 28.7 26.77 27.28 26.73 27.62 26.88 27.95 27.17 28.14
28.0 26.9 26.2 25.5 26.8 26.0 26.8 25.9 26.42 27.24 26.79 27.53 26.80 27.57 27.22 27.99
29.1 28.0 28.6 28.1 28.8 28.0 29.4 28.6 26.28 27.01 26.83 27.70 26.84 27.56 26.88 27.68
−20 29.7 28.7 28.7 28.0 29.1 28.2 30.1 29.3 26.15 26.88 26.65 27.49 26.95 27.73 26.86 27.93
29.6 28.2 29.6 28.6 29.5 28.3 29.6 28.7 26.41 27.36 26.34 27.26 26.33 27.37 26.75 27.69
29.8 28.5 29.0 28.0 29.3 28.8 29.8 29.1 26.52 27.40 26.85 27.80 26.60 27.46 27.06 27.99
Saline 2−8 29.8 28.9 29.3 28.6 29.0 28.2 29.1 28.3 26.77 27.65 26.98 27.91 26.92 27.80 27.31 28.30
30.0 28.9 29.5 28.7 28.6 27.5 29.8 29.2 26.48 27.47 27.06 28.00 27.14 28.10 27.41 28.41
29.7 28.7 29.3 28.9 29.7 28.9 29.9 29.1 25.99 27.07 27.06 28.03 27.28 28.30 27.42 28.47
−20 30.2 28.9 29.8 28.8 29.7 28.7 29.6 28.9 26.64 27.62 27.02 27.93 27.21 28.10 27.29 28.17
29.0 27.9 29.2 28.6 30.1 29.1 29.5 28.8 26.26 27.21 26.88 27.86 27.28 28.29 27.14 28.07
30.1 28.9 29.6 28.7 30.8 29.1 29.8 29.0 26.33 27.33 26.76 27.88 26.80 27.92 27.23 28.21
a

The nasopharyngeal samples were stored in M4-RT VTM, MEM, PBS, or saline. Twelve samples were created for each medium, allowing for testing of 3 unique samples per assay at both storage conditions. Abbreviations: M4, M4-RT VTM; LDT, laboratory-developed test; NUC, nucleocapsid target; ORF, open reading frame target; E, envelope target; CT, cycle threshold; MEM, minimum essential medium; PBS, phosphate-buffered saline without calcium and magnesium.