Prevalence of COVID-19 in patients with rheumatoid arthritis (RA) already treated with hydroxychloroquine (HCQ) compared with HCQ-naive patients with RA: a multicentre cross-sectional study
Khoubnasabjafari et al., Postgraduate Medical Journal, doi:10.1136/postgradmedj-2020-139561
https://c19hcq.org/khoubnasabjafari.html