The novel coronavirus disease 2019 (COVID-19) continues to spread internationally. Worldwide, almost 700 000 cases of coronavirus disease 2019 (COVID-19) (697 2744 ‘confirmed cases’ from Situation Dashboard WHO 30 March 2020), more than 33 000 deaths, and more than 100 000 recovered patients have been reported. The death rate estimated globally at 3.4% by the World Health Organization (WHO) varies between countries and across ages. Estimates of COVID-19 mortality rate per country rely on the number of deaths scaled to the number of confirmed COVID-19 cases. Since the denominator of the mortality rate should be the total number of patients diagnosed with the virus in a country, it will be nearly impossible to capture an accurate mortality rate for the time being. Therefore, the current mortality rate of COVID-19 might be skewed and may not allow for a direct comparison between countries. Furthermore, the WHO, the National Data, and other sources have provided a lot of data on the cumulative number of cases being placed as the denominator while estimating mortality rates. This may not be appropriate since testing strategies across countries vary. Some countries used the strategy of testing symptomatic individuals with probably a high viral shedding, while other countries also tested many asymptomatic people, leading to an increase in the number of cases. We would be tempted to accept the number of COVID-19 patients who require admission to hospitals as the denominator while estimating the current mortality rates of COVID-19. However, here again, caution is needed as the differences in rates may reflect the heterogeneity in: (i) the clinical management and care of COVID-19 patients which may vary across countries or (ii) the guideline of admission to hospital for patients with confirmed COVID-19. Overall, the final denominator to calculate the COVID-19 mortality rate may not be available or may be unknown for now. Therefore, comparison between countries should require other metrics such as: (i) the comparability between healthcare systems; (ii) the population size; (iii) the number of days since the date of the first diagnosed COVID-19 case; (iv) the heterogeneity in testing strategies across countries, for example testing symptomatic individuals in France with mostly a high viral shedding vs. testing asymptomatic individuals in South Korea or Germany; (v) the guidelines of admission to hospital for patients with confirmed COVID-19; and (vi) the variability in assessing the number of deaths per day, for example the number of deaths mentioned in France corresponds to the number of deaths in hospital. When a person not screened, in a EHPAD (collective retirement homes for dependent residents providing permanent medical services) or at home, dies she/he is not counted. Gathering information and recommendations, from researchers, physicians, other healthcare professionals, and administrators in hospitals and other clinical settings could help to alleviate this issue. (i) Guidelines of admission to hospital for patients with confirmed COVID-19. (ii) Clinical management and care of COVID-19 patients. (iii) Test kits used to detect COVID-19 and the number of tests per day. We are therefore pleased to invite sharing such information from around the world. This can be added as online comments to this article.

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分母在估计 COVID-19 死亡率方面很重要

2019 年新型冠状病毒病 (COVID-19) 继续在国际上蔓延。在全球范围内，已报告了近 70 万例 2019 年冠状病毒病 (COVID-19)（世卫组织情况仪表板中的 697 2744 例“确诊病例”，2020 年 3 月 30 日）、超过 33 000 例死亡和超过 10 万例康复患者。世界卫生组织 (WHO) 估计全球死亡率为 3.4%，因国家和年龄而异。每个国家/地区的 COVID-19 死亡率估计值取决于与确诊的 COVID-19 病例数成比例的死亡人数。由于死亡率的分母应该是一个国家确诊感染病毒的患者总数，因此目前几乎不可能获得准确的死亡率。所以，当前 COVID-19 的死亡率可能存在偏差，可能无法在国家之间进行直接比较。此外，世卫组织、国家数据和其他来源提供了大量关于在估计死亡率时将累计病例数作为分母的数据。这可能不合适，因为各国的测试策略各不相同。一些国家采用了对病毒排出量可能较高的有症状个体进行检测的策略，而其他国家也对许多无症状人群进行了检测，导致病例数增加。我们很想接受需要住院的 COVID-19 患者人数作为分母，同时估计 COVID-19 的当前死亡率。然而，在这里，需要谨慎，因为比率的差异可能反映了以下方面的异质性：(i) COVID-19 患者的临床管理和护理可能因国家/地区而异，或 (ii) 确诊 COVID-19 患者的住院指南。总体而言，计算 COVID-19 死亡率的最终分母可能无法获得或暂时未知。因此，国家之间的比较应该需要其他指标，例如：(i) 医疗保健系统之间的可比性；(ii) 人口规模；(iii) 自首例 COVID-19 确诊病例之日起的天数；(iv) 各国检测策略的异质性，例如在法国检测有症状的个体病毒脱落率高，而在韩国或德国检测无症状个体；(v) COVID-19 确诊患者入院指南；(vi) 评估每天死亡人数的可变性，例如法国提到的死亡人数对应于住院死亡人数。如果一个人在 EHPAD（为受抚养居民提供永久医疗服务的集体养老院）或在家中未进行筛查而死亡，则她/他不会被计算在内。从研究人员、医生、其他医疗保健专业人员以及医院和其他临床环境中的管理人员那里收集信息和建议可以帮助缓解这个问题。(i) COVID-19 确诊患者入院指南。(ii) COVID-19 患者的临床管理和护理。(iii) 用于检测 COVID-19 的测试套件和每天的测试次数。因此，我们很高兴邀请来自世界各地的分享此类信息。这可以作为在线评论添加到本文中。