Keogh Brad, Monks Thomas
NIHR CLAHRC Wessex Data Science Hub, Faculty of Environmental and Life Sciences, University of Southampton, Southampton, UK
NIHR CLAHRC Wessex Data Science Hub, Faculty of Environmental and Life Sciences, University of Southampton, Southampton, UK.
Emerg Med J. 2020 Feb;37(2):95-101. doi: 10.1136/emermed-2018-207917. Epub 2019 Nov 25.
There have been claims that Delayed Transfers of Care (DTOCs) of inpatients to home or a less acute setting are related to Emergency Department (ED) crowding. In particular DTOCs were associated with breaches of the UK 4-hour waiting time target in a previously published analysis. However, the analysis has major limitations by not adjusting for the longitudinal trend of the data. The aim of this work is to investigate whether the proposition that DTOCs impact the 4-hour target requires further research.
Estimation of an association between two or more variables that are measured over time requires specialised statistical methods. In this study, we performed two separate analyses. First, we created two sets of artificial data with no correlation. We then added an upward trend over time and again assessed for correlation. Second, we reproduced the simple linear regression of the original study using NHS England open data of English trusts between 2010 and 2016, assessing correlation of numbers of DTOCs and ED breaches of the 4-hour target. We then reanalysed the same data using standard time series methods to remove the trend before estimating an association.
After introducing upward trends into the uncorrelated artificial data the correlation between the two data sets increased (R=0.00 to 0.51 respectively). We found strong evidence of longitudinal trends within the NHS data of ED breaches and DTOCs. After removal of the trends the R reduced from 0.50 to 0.01.
Our reanalysis found weak correlation between numbers of DTOCs and ED 4-hour target breaches. Our study does indicate that there is no relationship between 4-hour target and DTOCs, it highlights that statistically robust evidence for this relationship does not currently exist. Further work is required to understand the relationship between breaches of the 4-hour target and numbers of DTOCs.
有人声称，住院患者延迟转至家中或病情较轻的机构与急诊科（ED）拥挤有关。特别是，在之前发表的一项分析中，延迟转院与违反英国4小时等待时间目标有关。然而，该分析存在重大局限性，未对数据的纵向趋势进行调整。这项工作的目的是调查延迟转院影响4小时目标这一命题是否需要进一步研究。
估计两个或多个随时间测量的变量之间的关联需要专门的统计方法。在本研究中，我们进行了两项独立分析。首先，我们创建了两组无相关性的人工数据。然后，我们随时间添加了上升趋势，并再次评估相关性。其次，我们使用2010年至2016年英格兰国民保健服务（NHS）开放数据，对原研究进行简单线性回归，评估延迟转院数量与急诊科违反4小时目标之间的相关性。然后，我们使用标准时间序列方法重新分析相同数据，以消除趋势，再估计关联。
在将上升趋势引入不相关的人工数据后，两个数据集之间的相关性增加（分别从R = 0.00增至0.51）。我们在NHS数据中发现了急诊科违反目标和延迟转院的纵向趋势的有力证据。去除趋势后，R从0.50降至0.01。
我们的重新分析发现延迟转院数量与急诊科4小时目标违反情况之间的相关性较弱。我们研究并未表明4小时目标与延迟转院之间存在关系，而是强调目前不存在关于这种关系的统计学上有力的证据。需要进一步开展工作来了解4小时目标违反情况与延迟转院数量之间的关系。
