TABLE 1.

Median C_T values for N1 and N2 targets^a

Storage condition by target and titer	Median CT value
	Day 0	Day 1	Day 2	Day 7	Day 14	Day 21	Day 28
N1
5,000–10,000 copies/ml
Room temp	31.4	31.0	31.5	31.2	31.6	31.4	31.3
4°C	30.8	30.9	31.3	31.5	31.7	31.5	31.4
−20°C	30.9	31.4	31.7	31.2	31.7	31.8	31.8
−80°C	30.7	31.1	31.4	31.0	31.0	30.9	31.8
500–1,000 copies/ml
Room temp	33.4	36.8	36.3	36.1 (3/4)b	35.8 (3/4)	35.2 (1/4)	NDET (0/4)
4°C	34.4	34.9	35.1	35.9	35.9	35.8 (3/4)	36.5
−20°C	34.2	35.2	36.0	36.5	37.5 (1/4)	37.4	37.3 (3/4)
−80°C	35.1	34.4	35.3	34.9	36.2	36.4	35.3
N2
5,000–10,000 copies/ml
Room temp	30.6	30.4	30.9	30.9	31.1	31.1	31.2
4°C	30.4	30.2	30.5	30.6	31.3	30.6	31.1
−20°C	30.6	30.5	30.9	30.6	31.6	30.9	31.2
−80°C	30.6	30.5	30.6	30.6	30.6	30.5	31.2
500–1,000 copies/ml
Room temp	32.8	35.0	35.8	36.6 (3/4)	37.0	38.3 (2/4)	38.3 (3/4)
4°C	33.8	34.2	34.7	34.9 (3/4)	36.0	35.4	36.4
−20°C	33.7	35.3	36.0	37.8 (3/4)	36.7	36.3 (3/4)	37.0 (3/4)
−80°C	34.4	33.7	34.8	35.7	35.8	34.7	35.9

^aC_T, cycle threshold; NDET, not detected. N1 and N2 are amplicons within the nucleocapsid gene of SARS-CoV-2.

^bParentheticals denote the number of samples that were detected at a condition only if the 4 replicates were not all detected.