Systematic Testing for SARS-CoV-2 Infection Among Essential Workers in Montréal, Canada: A Prospective Observational and Cost Assessment Study
Bibliographic record
Abstract
Abstract BACKGROUND Essential workers are at increased risk of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). We did a prospective study to estimate the yield, acceptability, and costs of workplace-based systematic SARS-CoV-2 testing of asymptomatic essential workers. METHODS We recruited non-healthcare essential businesses, in Montréal, Canada. Mobile teams, composed of two non-healthcare professionals each, visited businesses. Consenting, asymptomatic employees provided saline gargle specimens under supervision. Mobile team members self-sampled weekly. Specimens were analyzed using reverse-transcription polymerase chain reaction (RT-PCR). If an outbreak was detected (≥2 positives), we retested all initially negative participants. We did logistic regression for factors associated with a positive test. We estimated costs ($CAD) of this strategy. RESULTS From 27 January to 12 March 2021, 69 essential businesses were visited. Of an estimated 2348 employees onsite, 2128 (90.6%) participated. Across 2626 tests, 53 (2.0%) were positive. Self-reported non-Caucasian ethnicity (aOR 3.7, 95% CI: 1.4-9.9) and a negative SARS-CoV-2 test before the study (0.4, 0.2-0.8) were positively and negatively associated with a positive test, respectively. Five businesses—3 manufacturing/supplier and 2 meat processing— were experiencing an outbreak. At these businesses, 40 (4.4%) of 917 participants were positive on the initial test. We repeated testing at three of these businesses over 2-3 weeks: 8/350 (2.3%) were positive on the second test, and zero were positive on the third and fourth test (148 tests); no employer reported new positives to 26 March 2021. In all other businesses, 1211 participants were tested once—5 (0.4%) were positive at three childcare enterprises, one grocery store, and one manufacturing/supplier. Per person, RT-PCR costs were $34.00 and all other costs $8.67. No mobile team member tested positive. INTERPRETATION Onsite sampling of essential workers with saline gargle is safe, acceptable, and inexpensive. Repeat testing appeared to eliminate outbreaks. Systematic testing should be considered part of SARS-CoV-2 preventive efforts.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.003 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.001 |
| Bibliometrics | 0.001 | 0.003 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.002 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".