Observational data during the COVID-19 pandemic: opportunity with uncertainty

This editorial refers to ‘Risk of Severe COVID-19 disease associated with angiotensin converting enzyme inhibitors (ACEi) and angiotensin receptor blockers (ARB) in England: population cohort study including 8.3 million people’ by Hippisley et al published in Heart (2020).1

The exponential growth of the coronavirus disease 2019 (COVID-19) pandemic has led to an unprecedented hunger for information in the medical community, the media and the wider public. In response, there has been an explosion of publications including more than 21 000 references on PubMed to ‘COVID-19’ since January 2020. Many of these are observational data of hospitalised patients infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), exploring demographics or proposed risk factors including pre-existent cardiovascular disease (including diabetes mellitus),2 obesity3 and non-white ethnicity.4 The low rate of testing in communities in many countries (including the UK) means that data are mostly limited to hospitalised patients such that a valid picture of risk and outcomes relevant to the wider population is difficult to establish. Specifically, there remains uncertainty about the role of medications inhibiting the renin-angiotensin-aldosterone system (RAAS), based on initial reports of their association with poor outcomes in COVID-19.5 Possible explanations for this include underlying cardiovascular comorbidities in patients taking these medications and that the entry of SARS-CoV-2 into cells is permitted by the angiotensin-converting enzyme 2 receptor.6