Supplementary Table 1.
Included Studies on Prevalence of Asymptomatic Infection
| First author, year, design, setting, dates | Local prevalence | Symptom screening |
Testing strategy |
||||
|---|---|---|---|---|---|---|---|
| Type of screening | Positive screening | Type of test,timing of test | Positive asymptomatic cases, n | Total cases, n | Asymptomatic prevalence, % | ||
| Bowyer, 20219 Retrospective United States (IL) 5/22/20–6/28/20 |
8.4% local positivity rate for Winnebago County, IL between 9/1/20 and 9/9/20 | ASGE preprocedure risk screening questionnaire | 122/1000 = 12.2% positive Of those, 3 of 122 (2.46%) were SARS-CoV–positive |
NP swab Roche COBAS 6800/8800 RT-PCR 72 h prior |
5 | 878 | 0.57 |
| Casper, 202010 Retrospective Germany 3/23/20–5/10/20 |
Cumulative incidence in Saarland: 279 per 100,000 During study period, 2514 tested positive in Saarland |
Symptom screeninga | NR | NP swab RT-PCR Testing for all outpatients starting April 2020 <5 d prior |
0 | 313 | 0 |
| Haidar, 202113 Prospective United States (PA, NY) Period 1: April 21, 2020–June 11, 2020 Period 2: June 12, 2020–September 10, 2020 Period 3: September 11, 2020–December 15, 2020 (universal testing deimplemented) |
Total new cases in Allegheny County: Period 1: 1056 Period 2: 10,014 Period 3: 30,524 |
Symptom screening: fever, cough, and shortness of breath, and asked to self-report other symptoms <7 d of procedure, 1–4 d prior, and day of procedure | 16/817 (1.9%) | NP swab Cepheid Xpert Xpress RT-PCR 1–4 d preprocedure with results in <24 h with a subset of negative patients randomly selected for repeat testing on the same day of the procedure (with results <1 h) |
Period 1: 10 Period 2: 54 Period 3: 101 |
Period 1: 10,539 Period 2: 34,948 (“summer surge”) Period 3: 24,741 (“fall surge”) |
Period 1: 0.10 Period 2: 0.15 Period 3: 0.41 |
| Hernandez Camba, 202116 Retrospective Spain 4/27/20–6/15/20 |
NR | Screening questionnaire (fever, cough, sore throat, or breathing problems, known exposure, and loss of smell or taste) 3 d prior and 14 d after |
0/211: 0% | SARS-CoV2 antibody test followed by RT-PCR if positive only within 48 h | 0a | 211 | 0 |
| Lewis, 202117,b Retrospective United States (NC) 3/31/2020–4/20/2020 |
NR | Symptom screeningc | NR | 5 in-house tests: CDC’s 2019-nCOV RT-PCR diagnostic panel, Diasorin Simplexa COVID-19 direct assay, Cepheid Xpert Xpress, Abbott real-time SARS-CoV02 assay, Abbott ID NOW 72 h prior |
6 | 1580 | 0.4 |
| Tworek, 202119 Retrospective United States (MI) 4/15/20–5/15/20 |
NR | Symptom screeningc 2 d prior |
NR | ID NOW RT-PCR (gold standard) |
ID NOW: 0 RT-PCR: 3 |
386 | IDNow: 0 RT-PCR 0.77 |
| Hayee, 202115 Multicenter prospective study United Kingdom 4/30/2020–6/30/2020 |
NR | Telephone screening (SCOTS: questions on symptoms, infectious contacts, occupational risk, travel, shielding status |
NR | NP swab Type of test NR |
3 | 2611 | 0.11 |
| Hayee, 202114 Multicenter prospective study United Kingdom |
Rising incidence after emergence of new UK variant: at least 800 cases per 100,000 population per week |
Telephone screening (SCOTS: questions on symptoms, infectious contacts, occupational risk, travel, shielding status |
NR | NP swab Type of test NR |
9 | 2449 | 0.37 |
| Mays, 202018 Cross-sectional United States (University of Washington) 4/13/20 |
2-5% region prevalence |
Symptom screeninga | 137/133 6 (10.3%) |
PCR testing (DiaSorin Simplexa SARS-COV-2, Hologic Panther Fusion, or Roche COBAS) prior admission or surgical procedure | 5 | 787 | 0.6 |
| Albendin-Iglesias, 20208 Prospective observational cross-sectional Spain 4/15/20–5/15/20 |
3.34/100,000 between May 1 and May 15, 2020 | NR | NR | NP or OP with Allplex 2019-nCoV Assay (Seegene, Seoul, South Korea) | 21 | 363 | 0.27 |
| Dolinger, 202011 Retrospective single center study United States (NY City) 5/1/20–6/30/20 |
May NY State prevalence 5.34% and NY City 6.27% June NY State prevalence 1.20% and NY City 1.43% |
NR | NR | PCR testing 48–72 h before procedures | 6 | 623 | 0.96 |
| Gawron, 2021 (personal communication) Retrospective multicenter VAHCS United States 3/18/20–12/31/20 |
NR | Symptom screening (flu, cough, fever), travel history, known exposure 7 d before endoscopy |
2497/57,892 869 PCR-positive (1.5%) |
RT-PCR within 7 d of procedure | 106 | 129,410 92,030 |
0.1 |
| Forde, 202012 Retrospective single center study United States (FL) |
Miami-Dade County: 12.7%. In system’s catchment area: 5.4%–9.5% |
Symptom screening (fever, conjunctivitis, cough, sore throat, difficulty breathing, diarrhea, body aches, or lack of smell or taste in the last 3 d), travel history, known exposure 7–9 d prior, and on day of procedure |
NR | CE-IVD kit Gene-Finder COVID-19 Plus RealAmp Kit, QIAstat-Dx Respiratory 2019-nCoV- 2, and Cepheid Xpert Xpress SARS-CoV-2 |
1 | 396 | 0.25% |
ASGE, American Society for Gastrointestinal Endoscopy; NP, nasopharyngeal; OP, oropharyngeal; VAHCS, Veterans Affairs Health Care System.
a
In this study, antibody testing was used instead of RT-PCR. If IgM-positive, SARS-CoV-2 PCR testing was conducted. If positive, endoscopy was postponed. If negative, PCR was repeated and if negative again, endoscopy was performed. In this study, 1.9% (4 of 211) patients (95% CI, 0.07%–4.8%) were positive for SARS-CoV-2 antibodies, which does not indicate active infection; asymptomatic prevalence was 0% (RT-PCR was negative in the 4 patients with positive antibody testing)
b
In the study, pre-procedure testing included all ambulatory procedures, encompassing endoscopy. If cases were urgent, providers wore N95s/PAPRs if COVID status was unknown.
c
Symptom screening indicates that authors reported using symptom screening but provided no details as to the type of screening tool or questions.