This is a summary, written by members of the CITF Secretariat, of:

Davis P, Rosychuk R, Hau JP, Cheng I, McRae AD, Daoust R, Lang E, Turner J, Khangura J, Fok PT, Stachura M, Brar B, Hohl CM. Diagnostic yield of screening for SARS-CoV-2 among patients admitted to hospital for alternate diagnoses: an observational cohort study. BMJ Open. 2022 July 12. doi: 10.1136/ bmjopen-2021-057852.

The results and/or conclusions contained in the article do not necessarily reflect the views of all CITF members.

A CITF-funded study, published in BMJ Open, found that universal COVID-19 screening among adults admitted to hospital over two waves in 2020 with a diagnosis unrelated to COVID-19 had a low diagnostic yield, meaning universal screening, at the time, would not have been justifiable as a blanket policy. The study was led by Dr. Philip Davis (University of Saskatchewan) and Dr. Corinne Hohl (University of British Columbia).

For this observational study, data were examined for 15,690 eligible adults from the Canadian COVID-19 Emergency Department Rapid Response Network registry, across 30 acute care hospitals. Participants were patients who had been hospitalized for non-COVID-19 related diagnoses and tested for SARS-CoV-2 between March 1 and December 29, 2020. The primary outcome evaluated was a positive nucleic acid amplification test (NAAT) for SARS-CoV-2.

The 15,690 participants were divided into two groups:

  • Those without any COVID-19 compatible symptoms (compatible symptoms included cough, chest pain, loss of smell/taste, vomiting, headache).
  • Those with COVID-19 compatible symptoms that were attributed to an alternate diagnosis (e.g., congestive heart failure, chronic obstructive pulmonary disease).

Key findings:

  • Of the 3,113 patients admitted without COVID-19 compatible symptoms, 13 (0.4%) tested positive for COVID-19.
  • Of the 12,570 patients admitted with COVID-19 compatible symptoms, 109 (0.9%) tested positive for COVID-19.
  • This total of 122 patients testing positive for COVID-19 resulted in a diagnostic yield of 0.8%.
  • Patient factors that were associated with a greater risk of testing positive included presence of fever, being a healthcare worker, having a positive household contact or institutional exposure, and living in an area with a higher seven-day average incidence of COVID-19 cases.

The researchers only looked at NAAT and did not consider the diagnostic yield of antigen-based COVID-19 tests. Rapid antigen testing (RAT) was not widespread at the time of the study. They were also unable to define false positives based on the sensitivity and specificity of NAATs, which may have led to an overestimation of the diagnostic yield. The study was conducted at a time before either vaccines or repeat infections were widespread, and before the spread of other important SARS-CoV-2 variants, such as highly transmissible Omicron, so the context for universal screening was different.

However, the study did use data from a large pan-Canadian registry that included participants who were geographically and culturally diverse, which the researchers believe make the findings generalizable outside of the Canadian context.