标准化死亡率通常用作衡量医院绩效和质量的指标。此类度量可能,然而,如果入院阈值不同且未完全测量患者严重程度,则应有偏见。
为了检查医院死亡率的比较是否由于入院率的变化而存在选择偏差,使用按星期几变化的例子。
2013年4月1日至2014年2月28日期间,英格兰国家卫生局所有急性非专科医院的急诊科就诊人数为12,900,687人,计划外入院人数为3,418,446人。
基于人群的回顾性队列研究。使用患者水平的风险调整后的probit和双变量Heckman选择模型,将就诊后30天内的死亡率建模为周末或工作日出勤率以及入院率的医院水平预测因子的函数。通过使用不同的医院级别预测因子来支持稳健性。
当只检查被录取的人群时,与一周内入院的患者相比,周末入院的患者在30天内的死亡风险高出0.206个百分点.然而,周末到急诊科就诊的病人入院的概率低1.390个百分点.一旦考虑到这种选择偏差,周末对死亡率的影响减少了三分之二,死亡风险增加了0.068个百分点.
意外入院后标准化住院死亡率的比较可能会因急诊科入院率的变化而产生偏差。导致关于质量的不正确结论。因此,如果入院率不同且疾病严重程度未得到完全控制,使用死亡率作为绩效指标可能会导致误导性比较。如果要对医院绩效进行准确比较,则考虑样本选择偏差以及入院率和死亡率之间的依赖性至关重要。
Standardized mortality rates are routinely used as measures of hospital performance and quality. Such metrics may, however, be biased if hospital admission thresholds differ and patient severity is not fully measured.
To examine whether comparisons of hospital mortality rates suffer from selection bias due to variations in hospital admission rates, using the example of variations by day of the week.
12,900,687 emergency department attendances and 3,418,446 unplanned admissions to all acute non-specialist hospitals of the National Health Service in England between 1 April 2013 and 28 February 2014.
Population-based retrospective cohort
study. Mortality within 30 days of attendance is modelled as a function of weekend or weekday attendance and hospital-level predictors of admission rates using patient-level risk-adjusted probit and bivariate Heckman selection models. Robustness is supported by the use of different hospital-level predictors.
When examining only the admitted population, patients admitted to hospital at weekends have a 0.206 percentage point higher risk of death within 30 days compared to patients admitted during the week. However, patients attending emergency departments at weekends have a 1.390 percentage point lower probability of being admitted to hospital. Once this selection bias is accounted for, the weekend effect in mortality is reduced by two-thirds to a 0.068 percentage point increase in the risk of death.
Comparisons of standardized hospital mortality rates following unplanned admissions can be biased by variations in emergency department admission rates, leading to incorrect conclusions about quality. The use of mortality as a performance measure could therefore lead to misleading comparisons if admission rates vary and illness severity is not fully controlled for. Accounting for sample selection bias and dependence between admission and mortality rates is vital if accurate comparisons of hospital performance are to be made.