Material and Methods:
Design: This was a single-centre, prospective, randomised controlled cohort study. This study was conducted in the Health Sciences University Kanuni Sultan Suleyman Training and Research Hospital, which was designated as a pandemic hospital. The Ministry of Health and local ethics committee approved the study (Ethics Committee approval number: KAEK/2020.05.50).
Participants: Between March 7 and July 8, 2020, adults who were hospitalised in the pandemic ward with the diagnosis of COVID-19 included upon individual informed written consent. All participants evaluated with a nasopharyngeal swab polymerase chain reaction (PCR) and chest computed tomography (CCT). The treatment protocol recommended by the Ministry of Health was applied for all cases. The recommended treatment regimen is hydroxychloroquine, 400 mg daily for another 5 days, and/or favipiravir, 2 x 600 mg for 4 days following a 2 x 1600 mg loading dose on day one. QCB (1000 mg quercetin, 1000 mg vitamin C and 100 mg bromelain) supplementation was added daily in 2 divided doses to 52/447 patients with at least one chronic disease and moderate-to-severe respiratory symptoms. Computer-generated random numbers used for simple randomisation. Exclusion criteria determined as severe respiratory failure, shock and/or combined failure of other organs that required ICU monitoring and treatment; previous history of allergic reactions against any component of QCB; pregnant or lactating women; women of childbearing age with a positive pregnancy test, breastfeeding, miscarriage, or within 2 weeks after delivery; and participation in another clinical trial against SARS-CoV-2 treatment currently or in the past 28 days.
The study was reported according to the Consolidated Standards of Reporting Trials  guidelines and registered on ClinicalTrials.gov (number:  NCT04377789) on March 20, 2020. The primary endpoint of the study was determined as QCB supplementation was continued throughout the follow-up period from study baseline to discharge, intubation, or death. Demographic features, vital signs, laboratory test results during follow-up, drug administration data, past and current diagnoses of the patients were recorded. CCT findings of the cases were evaluated in 5 stages: stage 0 is the lung being completely normal, stage 1; light one-sided ground glass image, stage 2; multifocal double-sided ground glass image, stage 3; multifocal bilateral ground glass and stage 4; opacity, air bronchogram, bilateral ground glass and opacity, respectively.