Table 2.
Sensitivity of three commercial SARS-CoV-2 rapid antigen tests compared with RT-rtPCR and virus isolation
| Number of samples | Sensitivity vs RT-rtPCR (95% CI) | RNA copies per mL at 50% detection rate (95% CI) | N Ct value at 50% detection rate (95% CI) | ROC AUC (95% CI) | Number of samples | Sensitivity vs virus isolation (95% CI) | ||
|---|---|---|---|---|---|---|---|---|
| Encode | ||||||||
| Overall | 90† | 74·4% (64·6–82·3) | 1·31 × 105 (3·47 × 104–3·71 × 105) | 28·3 (26·9– 30·1) | 0·931 (0·879–0·984) | 34 | 100·0% (89·8–100·0) | |
| N Ct value <28 | 70 | 88·6% (79·0–94·1) | .. | .. | .. | .. | .. | |
| N Ct value <25 | 52 | 96·2% (87·0–99·3) | .. | .. | .. | .. | .. | |
| Subset* | 90 | 74·4% (64·6–82·3) | .. | .. | .. | .. | .. | |
| N Ct value <28 | 70 | 96·2% (87·0–99·3) | .. | .. | .. | .. | .. | |
| N Ct value <25 | 52 | 88·6% (79·0–94·1) | .. | .. | .. | .. | .. | |
| Innova | ||||||||
| Overall | 110† | 78·2% (69·6–84·9) | 1·31 × 105 (3·47 × 104–3·71 × 105) | 28·3 (26·9–30·1) | 0·931 (0·879–0·984) | 46 | 97·8% (88·7–99·9) | |
| N Ct value <28 | 88 | 92·0% (84·3–96·0) | .. | .. | .. | .. | .. | |
| N Ct value <25 | 66 | 97·0% (89·6–99·5) | .. | .. | .. | .. | .. | |
| Subset* | 90 | 76·7% (67·0–84·2) | 1·10 × 105 (3·31 × 104–2·82 × 105) | 28·6 (27·3–30·2) | 0·957 (0·919–0·996) | 34 | 100·0% (89·8–100·0) | |
| N Ct value <28 | 70 | 91·4% (82·5–96·0) | .. | .. | .. | .. | .. | |
| N Ct value <25 | 52 | 98·1% (89·9–99·9) | .. | .. | .. | .. | .. | |
| SureScreen-F | ||||||||
| Overall | 141 | 60·3% (52·0–68·0) | 1·38 × 106 (6·31 × 105–2·88 × 106) | 25·1 (24·1–26·2) | 0·918 (0·875–0·962) | 57 | 94·7% (85·6–98·6) | |
| N Ct value <28 | 111 | 74·8% (66·0–81·9) | .. | .. | .. | .. | .. | |
| N Ct value <25 | 82 | 84·2% (74·7–90·5) | .. | .. | .. | .. | .. | |
| Subset* | 90 | 55·6% (45·3–65·4) | 2·04 × 106 (8·12 × 105–4·68 × 106) | 24·6 (23·4–25·8) | 0·918 (0·864–0·971) | 34 | 100·0% (89·8–100·0) | |
| N Ct value <28 | 70 | 71·4% (60·0–80·7) | .. | .. | .. | .. | .. | |
| N Ct value <25 | 52 | 78·8% (66·0–87·8) | .. | .. | .. | .. | .. | |
SureScreen-F=SureScreen fluorescent. RT-rtPCR=real-time RT-PCR. N=SARS-CoV-2 nucleocapsid. Ct=cycle threshold. ROC=receiver operating characteristic. AUC=area under the curve.
Test results were re-analysed due to differences in sample number between Encode, Innova, and SureScreen-F (for the subset of samples available for all three tests: n=90 for sensitivity compared with RT-rtPCR, n=34 for sensitivity compared with virus isolation); two-tailed p values for these subsets, calculated with McNemar's test for all possible permutations, are shown in the appendix (p 5).
Due to insufficient sample volume or test unavailability, not all samples could be assayed on Innova and Encode.