Table 2.
Viral RNA From Cases Seronegative for SARS-CoV-2 Antibodies at the First Assessment
| Sample Type | Variant | Casea | Cases with ≥1 Positive Sampleb N (%) | Samples | Positive Samplesc N (%) | GM (95% CI) d | Maximum RNA Copiese | ||
|---|---|---|---|---|---|---|---|---|---|
| ≥LOD | ≥LOQ | ≥LOD | ≥LOQ | ||||||
| Mid-turbinate swab | Alpha | 4 | 4 (100) | 4 (100) | 6 | 6 (100) | 6 (100) | 3.8 × 108 (3.3 × 108, 4.4 × 108) | 2.9 × 109 |
| Other | 45 | 45(100) | 45 (100) | 74 | 74 (100) | 73 (99) | 3.8 × 106 (1.4 × 106, 1.0 × 107) | 5.1 × 109 | |
| Saliva | Alpha | 4 | 4 (100) | 4 (100) | 6 | 6 (100) | 6 (100) | 1.9 × 107 (2.7 × 106, 1.3 × 108) | 5.2 × 108 |
| Other | 45 | 44 (98) | 44 (98) | 74 | 73 (99) | 70 (95) | 2.1 × 105 (8.1 × 104, 5.4 × 105) | 3.9 × 108 | |
| Fomite | Alpha | 4 | 4 (100) | 4 (100) | 6 | 6 (100) | 4 (67) | 560 (530, 590) | 1.7 × 104 |
| Other | 45 | 28 (62) | 14 (31) | 74 | 36 (49) | 17 (23) | 46 (17, 120) | 1.2 × 106 | |
| Coarse (>5 µm) aerosol | Alpha | 4 | 4 (100) | 2 (50) | 6 | 6 (100) | 3 (50) | 140 (28, 730) | 5.1 × 104 |
| Other | 45 | 11 (24) | 5 (11) | 72 | 14 (19) | 5 (7) | 7 (3.2, 15) | 2.6 × 104 | |
| Fine (≤5 µm) aerosol | Alpha | 4 | 4 (100) | 3 (75) | 6 | 6 (100) | 4 (67) | 580 (450, 740) | 5.4 × 104 |
| Other | 45 | 18 (40) | 8 (18) | 72 | 22 (31) | 9 (12) | 18 (9.1, 34) | 2.8 × 103 | |
Abbreviations: GM, geometric mean; LOD, limit of detection; LOQ, limit of quantification; qRT-PCR, quantitative reverse transcription polymerase chain reaction; SARS-CoV-2, severe acute respiratory syndrome coronavirus 2.
aParticipants with a mid-turbinate or saliva samples positive for SARS-CoV-2 viral RNA by qRT-PCR and seronegative for SARS-CoV-2 spike protein antibody at enrollment and who provided at least one 30-minute sample of exhaled breath.
bNumber of participants with at least 1 sample ≥LOD or ≥ LOQ (Supplementary Materials).
cSamples positive and ≥LOD had at least 1 replicate with confirmed amplification after inspection and quality control (LOD ~75 RNA copies with 95% probability of detection) and ≥LOQ if the mean of replicate assays was ≥250 RNA copies.
dGMs were computed, accounting for samples below the LOD, using a linear mixed-effects model for censored responses (R Project lmec package) using data for all samples of each sample type with nested random effects of samples within study participant.
eThe largest quantity of RNA copies detected based on the mean of replicate qRT-PCR aliquots.