Apples & oranges: international comparisons of COVID-19 observational studies in ICUs
By Jonathan E Millar, Reinhard Busse, John F Fraser, Christian Karagiannidis and Daniel F McAuley
Published by The Lancet: Respiratory Medicine
Multiple observational cohorts describing the outcome of patients with COVID-19 from across the world have been published. (1-3) Typically, these studies have reported regional or national cohorts and no two countries have had the same experience. The reasons for these differences are complex and difficult to quantify. Nonetheless, to be able to draw meaningful inferences from these data we must tackle the issues associated with international comparison.
Initial reports of outcomes in COVID-19, which emerged from China early in the pandemic, reported a range of mortality rates from intensive care units (ICUs) (0–78%).(3) Case series from North America and Europe have been equally variable (with ICU mortality ranging 0–85%).(3) A major issue has been the large number of patients in these series who had incomplete outcomes at the time of reporting, a factor that has commonly resulted in mortality being overestimated or underestimated. For example, in UK Intensive Care National Audit and Research Centre (ICNARC) data, early reports from March, 2020, estimated ICU mortality for COVID-19 to be 79 (48%) of 165 patients admitted, when 610 (79%) of 775 patients had an incomplete outcome (ie, were still in the ICU).
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