Study of critically ill patients with COVID-19 in New York City
Authors: Daniele Piovani, Stefanos Bonovas
Journal: The Lancet (2020)

Cummings and colleagues1Cummings MJ Baldwin MR Abrams D et al.Epidemiology, clinical course, and outcomes of critically ill adults with COVID-19 in New York City: a prospective cohort study.Lancet. 2020; 395: 1763-1770Summary Full Text Full Text PDF PubMed Scopus (1500) Google Scholar reported the epidemiology, clinical course, and outcomes of 257 critically ill adults with laboratory-confirmed COVID-19 admitted to two hospitals in New York City. The primary outcome was the rate of in-hospital death, and each patient had at least 28 days of observation. The authors report that, as of April 28, 2020, 101 (39%) of 257 patients had died, 94 (37%) remained hospitalised, four (2%) were transferred to another hospital, and 58 (23%) were discharged alive. Surprisingly, the authors show in figure 1 of their Article1Cummings MJ Baldwin MR Abrams D et al.Epidemiology, clinical course, and outcomes of critically ill adults with COVID-19 in New York City: a prospective cohort study.Lancet. 2020; 395: 1763-1770Summary Full Text Full Text PDF PubMed Scopus (1500) Google Scholar a cumulative incidence of in-hospital death of approximately 45% at 28 days. Given the numbers of patients at risk reported below the figure, we have identified that this result is not correct. Apparently, the authors censored the patients discharged alive (n=58) at the day of discharge. This methodological error has led to overestimation of the cumulative incidence of death, and distorted the results of the Cox proportional hazards regression. A fundamental assumption in survival analysis is that censoring should be non-informative—ie, that patients censored have the same survival prospects as those who continue to be followed up.2Bland JM Altman DG Survival probabilities (the Kaplan–Meier method).BMJ. 1998; 3171572Crossref PubMed Google Scholar Patients discharged alive should not have been censored; their status should be considered as event-free (ie, alive) throughout the study observation period. This methodological error in the COVID-19 literature is common yet serious.3Bonovas S Piovani D Compassionate use of remdesivir in Covid-19.N Engl J Med. 2020; 382: e101Crossref Scopus (30) Google Scholar We kindly ask the authors to reanalyse the data, and correctly report the cumulative incidence, and the risk factors of in-hospital mortality, considering the above aspects. We declare no competing interests. Epidemiology, clinical course, and outcomes of critically ill adults with COVID-19 in New York City: a prospective cohort studyCritical illness among patients hospitalised with COVID-19 in New York City is common and associated with a high frequency of invasive mechanical ventilation, extrapulmonary organ dysfunction, and substantial in-hospital mortality. Full-Text PDF Study of critically ill patients with COVID-19 in New York City – Authors' replyWe agree with Daniele Piovani and Stephanos Bonovas that informative censoring, if present, could represent a potential source of bias in the survival analyses in our Article.1 However, sensitivity analysis suggests that any such bias is likely to be minimal. Full-Text PDF