STUDY DESIGN
DATA COLLECTION
The BQC19 routinely collects biological samples and clinical data during participant follow-up visits. However, in some cases, clinical constraints or health restrictions prevented the collection of samples. In these situations, priority was given to recording the associated clinical data, even in the absence of biological samples. This compromise preserves the richness of longitudinal information on participants, while adapting to specific contexts.
PARTICIPANTS WITH SEVERE DISEASE
BQC19 participants are identified in partnership with hospital clinical teams via an alert reporting a patient who has undergone PCR testing for SARS-CoV-2. Once identified, participants, or their legal representatives, are contacted by telephone or videoconference to propose their inclusion in the study. Following consent, hospital follow-up began with samples taken during standard care. Initial visits include days 0, 2 and 7, while follow-ups on days 14 and 30 were added after a revision of the management framework in June 2020. However, 30-day follow-ups remain limited for participants in the first pandemic wave. Visits are carried out throughout the patient’s hospital stay.
Participants hospitalized for severe COVID-19-related illness as part of the BQC19 can consent to a two-year longitudinal follow-up after discharge. Follow-up visits are scheduled at 1, 3, 6-, 12-, 18- and 24-months post-discharge. Although follow-up visits are scheduled at specific intervals, constraints linked to the epidemiological situation may lead to variations in the timing of these visits. A natural attrition in the number of participants followed up is observed, attributable to deaths and the difficulty of reaching certain participants residing in care settings such as residences for the elderly (RPA) or long-term care facilities (CHSLD).
Day 0
Recruitment.
Collection of blood samples and clinical data
Day 2
Collection of blood samples and clinical data
Day 7
Collection of blood samples and clinical data
Day 14
Collection of blood samples and clinical data
Day 30
Collection of blood samples and clinical data
PARTICIPANTS WITH MILD OR
ASYMPTOMATIC DISEASE
BQC19 includes a cohort of participants with mild or asymptomatic COVID-19, recruited from May 2020 onwards to reflect the evolution of the pandemic. These participants, who did not require hospitalization, include cases who tested positive or negative for SARS-CoV-2 PCR. Longitudinal follow-up, similar to that for hospitalized participants, begins one month after the PCR test, without initial sampling (day 0). Follow-up visits are scheduled at months 1, 3, 6, 12, 18 and 24 post-infection. This cohort aims to enrich our understanding of the less severe clinical trajectories of the disease.
LONG COVID
Clinical data and biological samples collected during longitudinal follow-up of patients with severe or mild disease are a valuable and invaluable resource for further understanding and study of long-standing COVID.
Day 30
Recruitment (participants with mild/asymptomatic disease)
Collection of blood samples and clinical data
Day 90
Collection of blood samples and clinical data
Day 180
Collection of blood samples and clinical data
Day 365
Collection of blood samples and clinical data
Day 540
Collection of blood samples and clinical data
Day 730
Collection of blood samples and clinical data