Table 1.
SARS-CoV-2 Cycle Threshold (Ct) Values, Number/Percent of Samples With Ct Values No More Than Ct 25 or Ct 30, and Nucleoprotein Antigen Concentrations, Grouped by Days Since Symptom Onset
| Days Since Symptom Onset | Ct, Median (IQR) | Ct ≤ 25, n (%) | Ct ≤ 30, n (%) | Ag Conc (pg/mL), Median (IQR), n |
|---|---|---|---|---|
| 0, n = 20 | 28.9 (23.9–33.5) | 6 (30) | 12 (60) | 8.2 (0.1–103.6), n = 15 |
| 1, n = 101 | 24.3 (19.6–29.4) | 54 (53.5) | 81 (80.2) | 26.6 (1.9–704.2), n = 79 |
| 2, n = 103 | 23.4 (18.6–30.7) | 61 (59.2) | 77 (74.8) | 46.6 (0.5–2614.4), n = 80 |
| 3, n = 60 | 20.8 (18.9–23.8) | 48 (80) | 56 (93.3) | 477.7 (103.6–2937.1), n = 43 |
| 4, n = 31 | 21.2 (18.9–24.1) | 25 (80.6) | 28 (90.3) | 688.5 (141.5–5270.8), n = 23 |
| 5, n = 14 | 26.6 (22.5–28.6) | 6 (42.9) | 12 (85.7) | 16.7 (2.2–26.5), n = 9 |
| 6, n = 9 | 25.9 (20.4–29.4) | 4 (44.4) | 7 (77.8) | 1002.1 (0.6–1756.4), n = 7 |
| 0–6, n = 338 | 23.4 (19.2–28.9) | 204 (60.4) | 273 (80.8) | 120 (2.8–1801), n = 256 |
| 7+, n = 10 | 31.4 (28.5–35.2) | 0 (0) | 4 (40) | 9.1 (0.3–21.8), n = 8 |
Abbreviations: Ag, antigen; Conc, concentration; Ct, cycle threshold; IQR, interquartile range.