Table 1.
LFD performance in SARS-CoV-2 PCR-positive samples (n=4131)
|
Summary |
Univariable |
Multivariable |
||||||
|---|---|---|---|---|---|---|---|---|
| LFD negative; n (%) or median (IQR); n=1522 | LFD positive; n (%) or median (IQR); n=2609 | Sensitivity (95% CI) | OR (95% CI) | p value | Adjusted OR (95% CI) | p value | ||
| Log10 viral load* | 3·84 (2·48–5·02) | 6·12 (5·29–6·80) | .. | 2·80 (2·63–2·98) | <0·0001 | 2·85 (2·66–3·06) | <0·0001 | |
| LFD type | ||||||||
| Innova | 1270 (38·7%) | 2008 (61·3%) | 61·3% (59·6–62·9) | 1 (ref) | .. | 1 (ref) | .. | |
| Acon | 70 (27·7%) | 183 (72·3%) | 72·3% (66·4–77·8) | 1·65 (1·24–2·20) | 0·0005 | 1·65 (0·96–2·83) | 0·070 | |
| Orient Gene | 182 (30·3%) | 418 (69·7%) | 69·7% (65·8–73·3) | 1·45 (1·20–1·75) | 0·0001 | 1·11 (0·78–1·57) | 0·56 | |
| Test setting | ||||||||
| Unselected community-based testing | 676 (28·4%) | 1705 (71·6%) | 71·6% (69·8–73·4) | 1 (ref) | .. | 1 (ref) | .. | |
| Health-care workers | 10 (35·7%) | 18 (64·3%) | 64·3% (44·1–81·4) | 0·71 (0·33–1·55) | 0·40 | 0·60 (0·14–2·50) | 0·48 | |
| Predeployment evaluation | 530 (47·2%) | 593 (52·8%) | 52·8% (49·8–55·8) | 0·44 (0·38–0·51) | <0·0001 | 0·51 (0·36–0·73) | 0·0002 | |
| Schools | 52 (58·4%) | 37 (41·6%) | 41·6% (31·2–52·5) | 0·28 (0·18–0·43) | <0·0001 | 0·70 (0·30–1·63) | 0·41 | |
| Targeted groups | 233 (50·1%) | 232 (49·9%) | 49·9% (45·3–54·5) | 0·39 (0·32–0·48) | <0·0001 | 0·51 (0·33–0·78) | 0·0018 | |
| Universities | 16 (42·1%) | 22 (57·9%) | 57·9% (40·8–73·7) | 0·55 (0·28–1·04) | 0·067 | 0·84 (0·31–2·33) | 0·74 | |
| Workplaces | 5 (71·4%) | 2 (28·6%) | 28·6% (3·7–71·0) | 0·16 (0·03–0·82) | 0·028 | 0·12 (0·01–1·86) | 0·13 | |
| Age† | 34 (25–47) | 36 (25–47) | .. | 1·00 (1·00–1·01) | 0·34 | 1·00 (0·99–1·00) | 0·41 | |
| Unknown‡ | 105 | 151 | NA | .. | .. | .. | .. | |
| Self-reported sex | ||||||||
| Female | 740 (35·9%) | 1323 (64·1%) | 64·1% (62·0–66·2) | 1 (ref) | .. | 1 (ref) | .. | |
| Male | 680 (37·4%) | 1139 (62·6%) | 62·6% (60·3–64·8) | 0·94 (0·82–1·07) | 0·33 | 0·89 (0·75–1·07) | 0·21 | |
| Unknown‡ | 102 | 147 | NA | .. | .. | .. | .. | |
| Assistance in interpreting test result | ||||||||
| Assisted | 602 (47·5%) | 665 (52·5%) | 52·5% (49·7–55·3) | 1 (ref) | .. | 1 (ref) | .. | |
| Self-interpreted | 920 (32·1%) | 1944 (67·9%) | 67·9% (66·1–69·6) | 1·91 (1·67–2·19) | <0·0001 | 0·79 (0·60–1·05) | 0·11 | |
| Symptom status | ||||||||
| Asymptomatic | 648 (47·2%) | 724 (52·8%) | 52·8% (50·1–55·4) | 1 (ref) | .. | 1 (ref) | .. | |
| Symptomatic | 847 (31·3%) | 1859 (68·7%) | 68·7% (66·9–70·4) | 1·96 (1·72–2·25) | <0·0001 | 1·63 (1·30–2·04) | <0·0001 | |
| Unknown‡ | 27 | 26 | NA | .. | .. | .. | .. | |
| Vaccination status | ||||||||
| Unvaccinated | 874 (42·7%) | 1171 (57·3%) | 57·3% (55·1–59·4) | 1 (ref) | .. | 1 (ref) | .. | |
| One dose | 163 (32·4%) | 340 (67·6%) | 67·6% (63·3–71·7) | 1·56 (1·27–1·91) | <0·0001 | 1·13 (0·81–1·57) | 0·48 | |
| Two or more doses | 471 (30·3%) | 1083 (69·7%) | 69·7% (67·3–72·0) | 1·72 (1·49–1·97) | <0·0001 | 1·13 (0·81–1·59) | 0·46 | |
| Unknown‡ | 14 | 15 | NA | .. | .. | .. | .. | |
| Assigned SARS-CoV-2 variant | ||||||||
| Alpha (B.1.1.7) or pre-alpha (B.1.177) | 674 (44·3%) | 846 (55·7%) | 55·7% (53·1–58·2) | 1 (ref) | .. | 1 (ref) | .. | |
| Delta (B.1.617.2) | 545 (36·0%) | 970 (64·0%) | 64·0% (61·6–66·4) | 1·42 (1·23–1·64) | <0·0001 | 1·00 (0·69–1·45) | 0·99 | |
| Omicron (BA.1 or BA.2) | 290 (27·0%) | 783 (73·0%) | 73·0% (70·2–75·6) | 2·15 (1·82–2·55) | <0·0001 | 1·63 (1·02–2·59) | 0·042 | |
| Other or unknown | 13 (56·5%) | 10 (43·5%) | 43·5% (23·2–65·5) | 0·61 (0·27–1·41) | 0·25 | 0·43 (0·15–1·23) | 0·12 | |
Denominators for percentages are the total number of LFD-negative and LFD-positive samples in each row. The logistic regression analyses show ORs for LFD positivity, such that higher ORs represent greater sensitivity. There was no evidence that adjusted models allowing for a non-linear relationship between the natural log odds of a positive result and log10 viral load or age (using splines with up to five knots) improved model fit based on the Bayesian information criterion. LFD=lateral flow device. n=number of samples. OR=odds ratio. NA=not applicable.
OR is for the odds of LFD positivity per 1 log10 copies per mL increase in viral load.
ORs per 1-year increase.
Data not summarised or analysed as there is no obvious interpretation.