Heterogeneity in testing, diagnosis and outcome in SARS-CoV-2 infection across outbreak settings in the Greater Toronto Area, Canada: an observational study

Note: CI = confidence interval, GTA = Greater Toronto Area, LTCH = long-term care home, NA = not available, OLIS = Ontario Laboratory Information System, SARS-CoV-2 = severe acute respiratory syndrome coronavirus 2.

↵* The population size of LTCH residents was approximated by the total LTCH bed capacity in the GTA; the population size of people using shelters was approximated by the estimated number of people experiencing homelessness in the GTA (Appendix 1, available at www.cmajopen.ca/content/8/4/E627/suppl/DC1); the population size of the rest of the population was estimated by the total census population size of the GTA (6 847 794) subtracting the population size of LTCH residents and people using shelters.

↵† Number of diagnosed cases and number of deaths were sourced from the Integrated Public Health Information System.

↵‡ Of 16 490 diagnosed cases, 112 LTCH residents, 4 people using shelters and 85 individuals from the rest of the population had unknown sex; of 918 deaths, 27 LTCH residents who died had unknown sex; sex distribution proportions are based on nonmissing information.

↵§ Number of individuals tested and number who tested positive were sourced from the OLIS.

↵¶ For individuals with multiple tests, we selected 1 testing episode per individual based on the following hierarchy: i.e., the earliest testing episode where the individual was confirmed positive for SARS-CoV-2 infection, or their earliest episode where the results were indeterminate, or earliest episode where the individual tested negative. (22) We considered individuals with only indeterminate results as positive as most individuals who had indeterminate results tested positive at a later date.

↵** Estimated using quasi-Poisson regression models, adjusting for age and sex.

↵†† Partial Wald tests (40) were performed to compare the difference in case-fatality rate and test positivity rate across settings estimated by the quasi-Poisson regression models.

↵‡‡ A total of 4.3% of confirmed cases had an unknown outcome by the end of follow-up and were considered alive in our calculation. Thus, our estimates could underestimate the case-fatality proportion.

↵§§ The overrepresentation of women among diagnosed cases of LTCH residents should not be interpreted as increased risk of diagnoses for female residents, as data among all LTCH in Ontario have shown that more than 75% of LTCH beds are occupied by women. (27) Similarly, around 43.4% of people using shelters are female (Appendix 1) and 50.9% of the GTA population are female. (3)

↵¶¶ We did not show results pertaining to testing for people using shelters owing to low sensitivity in identifying people using shelters in the OLIS testing data. A total of 1398 individuals had an indication of “homelessness” in OLIS data and had at least 1 test for SARS-CoV-2 infection, comprising 13.2% of people using shelters in the GTA. Of these 1398 individuals who may use shelters, 6.4% tested positive, comprising 24% of all diagnosed cases of SARS-CoV-2 infection in shelters by May 20, 2020.