Hydroxychloroquine as a primary prophylactic agent against SARS-CoV-2 infection: A cohort study.

OBJECTIVE: Hydroxychloroquine has been proposed as a primary prophylactic agent against coronavirus disease 2019 (COVID-19). This study aimed to investigate if patients treated with hydroxychloroquine for a non-COVID-19 indication had a lower risk of verified infection with severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) compared with matched controls. METHODS: A cohort comprising all persons in Denmark collecting hydroxychloroquine prescriptions in 2020 and 2019 (i.e., both during and before SARS-CoV-2 was confirmed in Denmark), matched by age and sex with controls, was studied. Data were collected using the Danish national registries, which contain complete information on patient health data, prescriptions and microbiological test results. The main outcome was microbiologically verified SARS-CoV-2 infection. RESULTS: In total, 5488 hydroxychloroquine users were matched with 54,486 non-users. At baseline, the groups differed in terms of diagnoses of pulmonary disease, cardiovascular disease, renal disease, gastrointestinal/metabolic disease and dementia, as well as treatment with antirheumatic drugs. The final model was adjusted for these potential confounders. Use of hydroxychloroquine for non-COVID-19 indications was not associated with any change in confirmed SARS-CoV-2 (hazard ratio 0.90, 95% confidence interval 0.76-1.07). This result was robust in the propensity-score-matched sensitivity analysis. CONCLUSION: This study, which is the largest to date to investigate the primary prophylactic effect of hydroxychloroquine against SARS-CoV-2, does not support any prophylactic benefit of hydroxychloroquine in the prevention of infection with SARS-CoV-2.

Silent hypoxia in patients with SARS CoV-2 infection before hospital discharge.

OBJECTIVE: To assess the degree of hypoxia and subjective dyspnea elicited by a 6-minute walking test (6MWT) in COVID-19 patients prior to discharge. METHODS: A 6MWT was performed in 26 discharge-ready COVID-19 patients without chronic pulmonary disease or cardiac failure. Heart rate, oxyhemoglobin saturation (SpO2), respiratory rate, and subjective dyspnea measured on the Borg CR-10 scale were measured before and immediately after the 6MWT, with continuous monitoring of SpO2 and heart rate during the 6MWT. The 6MWT was terminated if SpO2 dropped below 90%. A historical cohort of 204 patients with idiopathic pulmonary fibrosis (IPF) was used for comparison. RESULTS: 13 (50%) of the COVID-19 patients developed exercise-induced hypoxia (SpO2 < 90%) during the 6MWT, of which one third had pulmonary embolism. COVID-19 patients experienced less hypoxia-related dyspnea during the 6MWT compared with patients with IPF. CONCLUSION: The 6MWT is a potential tool in the diagnosis of asymptomatic exercise-induced hypoxia in hospitalized COVID-19 patients prior to discharge. Due to important methodological limitations, further studies are needed to confirm our findings and to investigate their clinical consequences.