Study design
The project
The Biobanque québécoise de la COVID-19 (BQC 19) is a prospective, observational, case-control and multicentre cohort study carried out at 10 test sites in Quebec. All BQC19 sites adhere to the Management Framework, procedures manual and Standard Operating Procedures that have been developed for the study.
The project has adjusted to new conditions as the pandemic situation has evolved in Quebec. So, while in April of 2020 the participants recruited by the sites were individuals who had been hospitalized due to severe illness, as of May of 2020 the project began to include patients who were moderately affected or asymptomatic. Participants have been recruited to the BQC19 from each succeeding pandemic wave that has manifested itself in Quebec.
The BQC19’s mission is to contribute to research that aims to identify the clinical and molecular determinants for susceptibility to, severity of and consequences of COVID-19.
In each participant visit, complete clinical data is harvested, as well as samples, where appropriate.
The cohort
The BQC19 cohort includes participants who have been hospitalized with moderate to severe illness, as well as participants with mild illness or who are asymptomatic, all infected with SARS-CoV-2 (cases). It also includes participants who have not been infected with SARS-CoV-2 (control subjects). For all participants, the classification is based on the result of a PCR test.
The cohort also has a pediatric sub-population recruited according to the criteria used in the study Biobanque d’échantillons et de données pour la recherche sur les maladies respiratoires pédiatriques (A biobank of samples and data for research into pediatric respiratory illnesses) conducted by Dr. Sze Man Tse (pediatrician at CHU Sainte-Justine).
As of November 5, 2021, more than 3,400 participants had been recruited. For more information on the BQC19’s cohort as a whole, see "BQC19 in numbers".
Mild illness / asymptomatic
This population is recruited in outpatient clinics or post-COVID clinics. It includes participants who have experienced mild illness or who have been asymptomatic. Some of these individuals present post-COVID symptoms.
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Five sites recruit this population.
Severe illness
This population is sought out in hospital settings. It includes participants who needed to be hospitalized due to COVID-19. These individuals were recruited during a stay in a COVID unit or in intensive care, in accordance with the BQC19’s procedures manual.
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The BQC19 recruits this population at 10 sites.
Control population
The BQC19 also recruits a control population of individuals who have not had COVID-19. This control population includes participants who have been hospitalized (either in a COVID unit or intensive care) and participants who have not been hospitalized but who present symptoms resembling those of COVID-19, yet were declared negative for SARS-CoV-2 subsequent to a PCR test.
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The BQC19 recruits this population at 10 sites.
Pediatric/obstetrical population
The BQC19 also includes a sub-population of pediatric participants, and some patients who are pregnant. This cohort is quite limited since, up to this point, the pandemic has not affected children to a great extent.
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These participants are mainly recruited at CHU Sainte-Justine.
Study design
The BQC19 collects samples and clinical data through the duration of follow-up with the participant. However, in some cases, samples could not be collected, due to particular clinical conditions, or health measures that were then in effect. In these situations, priority was thus given to the collection of data, even if no associated sample could be collected.
Hospitalization – severely ill participants
The initial identification of participants was carried out in collaboration with clinical teams in the hospital settings. An alert was sent to the BQC19 teams noting the arrival of a patient who had undergone a PCR screening test for SARS-CoV-2. Subsequently, the participant, or their legal representative, was contacted by phone or by videoconference and asked to be involved in the study.
Once the participant was enrolled, in-hospital tracking could begin. The samples collected by the BQC19 were taken during the sampling that was part of the patient’s regular care. "Hospital visits" occurred on the day of recruitment (Day 0), Day 2 and Day 7. It was only when the Management Framework was updated in June of 2020 that Day 14 and Day 30 follow-ups were added. Therefore, BQC19 has very few instances of 30-day monitoring for participants from the first COVID wave. Follow-ups were carried out on the day specified in the project, so long as the participant remained in hospital.
Longitudinal study - participants with severe illness
Patients who have been enrolled while in a hospital setting may also consent to a follow-up during the two years after their discharge. Follow-up visits occur 1, 3, 6, 12, 18 and 24 months following the departure from hospital. These follow-ups are carried out at the prescribed date when possible, but the epidemiological situation may prevent them from occurring in the desired time period.
We have observed a natural attrition in the number of participants being followed, due to mortality and sometimes attributable to difficulties in reaching participants living in certain care settings (RPA, CHSLD).
Longitudinal study - participants with mild illness / asymptomatic
The BQC19 also includes a cohort of participants who did not require hospital services. This cohort reflected the pandemic’s evolution in the spring of 2020, where it was observed that a segment of the population infected with SARS-CoV-2 developed few or no symptoms. This cohort was added in May of 2020.
The timing of visits is the same as for hospitalized patients, with the exception of the sampling on Day 0. For this cohort, follow-ups begin a month after the SARS-CoV-2 PCR screening test. The cohort has participants who have received either positive or negative tests for SARS-CoV-2.