Table 3.
Relative performance of point-of-care test compared with immunoassay for detection of IgG antibodies for SARS-CoV-2
| Number of participants | Seroprevalence with immunoassay (95% CI) |
Point-of-care test |
||||
|---|---|---|---|---|---|---|
| Relative sensitivity (95% CI) | Relative specificity (95% CI) | |||||
| Overall | 51 958 | 4·6% (4·3–5·0) | 79·6% (77·1–81·8) | 98·3% (98·2–98·5) | ||
| Sex | ||||||
| Female | 27 141 | 4·6% (4·2–5·0) | 80·1% (76·7–83·1) | 98·3% (98·1–98·6) | ||
| Male | 24 817 | 4·6% (4·2–5·0) | 79·0% (75·5–82·2) | 98·3% (98·1–98·5) | ||
| Age, years | ||||||
| 0–19 | 6527 | 3·8% (3·2–4·6) | 82·4% (75·1–88·0) | 98·9% (98·5–99·2) | ||
| 20–34 | 7569 | 5·0% (4·3–5·8) | 71·5% (64·1–77·9) | 98·9% (98·5–99·2) | ||
| 35–49 | 13 354 | 4·9% (4·3–5·5) | 78·4% (73·4–82·6) | 98·3% (98·0–98·6) | ||
| 50–64 | 13 906 | 4·7% (4·1–5·3) | 83·4% (79·3–86·8) | 98·0% (97·6–98·3) | ||
| ≥65 | 10 602 | 4·5% (3·8–5·3) | 82·3% (77·1–86·5) | 97·6% (97·2–98·0) | ||
| Census tract income* | ||||||
| <5th percentile | 2382 | 4·6% (3·1–6·7) | 75·7% (62·4–85·4) | 97·9% (96·5–98·8) | ||
| 5th to <25th percentile | 11 229 | 4·7% (3·8–5·8) | 82·2% (77·2–86·3) | 98·6% (98·3–98·9) | ||
| 25th to <50th percentile | 13 096 | 4·6% (3·9–5·6) | 78·3% (73·3–82·5) | 98·3% (97·9–98·6) | ||
| 50th to <75th percentile | 11 804 | 4·3% (3·6–5·1) | 77·9% (71·4–83·3) | 98·3% (97·9–98·6) | ||
| 75th to <95th percentile | 10 583 | 4·6% (3·7–5·7) | 79·5% (73·9–84·1) | 98·3% (97·9–98·6) | ||
| ≥95th percentile | 2864 | 5·4% (4·0–7·4) | 85·3% (74·7–92·0) | 98·1% (97·2–98·6) | ||
| Self-reported symptoms† | ||||||
| Asymptomatic | 34 016 | 2·0% (1·8–2·3) | 61·0% (55·8–65·9) | 98·6% (98·4–98·7) | ||
| Paucisymptomatic | 10 669 | 3·9% (3·4–4·4) | 76·4% (70·0–81·7) | 98·3% (97·9–98·6) | ||
| Symptomatic | ||||||
| ≤14 days before study visit | 2155 | 14·0% (11·8–16·5) | 85·3% (78·7–90·1) | 97·3% (96·1–98·2) | ||
| >14 days before study visit | 5118 | 18·0% (16·3–19·9) | 92·0% (89·1–94·1) | 97·0% (96·1–97·7) | ||
| Self-reported PCR status | ||||||
| Never done | 50 594 | 4·2% (3·8–4·5) | 78·0% (75·3–80·4) | 98·3% (98·2–98·5) | ||
| Negative | 1134 | 8·0% (6·0–10·6) | 82·0% (70·7–89·6) | 98·5% (97·5–99·1) | ||
| Positive (≤14 days before study visit) | 31 | 65·8% (41·5–83·9) | 76·4% (33·2–95·5) | 98·3% (87·8–99·8) | ||
| Positive (>14 days before study visit) | 195 | 90·1% (84·3–93·9) | 97·2% (91·7–99·1) | 82·4% (59·7–93·7) | ||
Relative performance is among 51 958 participants with both point-of-care test and immunoassay. SARS-CoV-2=severe acute respiratory syndrome coronavirus 2.
*
Categories based on percentiles from province-specific distributions of census tract average income in 2017.
†
Asymptomatic (no symptoms), paucisymptomatic (1–2 symptoms without anosmia or ageusia), and symptomatic (anosmia or ageusia, or at least three symptoms among fever; chills; severe tiredness; sore throat; cough; shortness of breath; headache; or nausea, vomiting, or diarrhoea).