Hankey G J, Dennis M S, Slattery J M, Warlow C P
Department of Neurology, Royal Perth Hospital, Western Australia.
BMJ. 1993 Apr 24;306(6885):1107-11. doi: 10.1136/bmj.306.6885.1107.
The outcomes of each of three large cohorts of patients with transient ischaemic attacks, which were studied in the same country at much the same time with the same methods, were compared and found to be quite different from each other. The differences in outcome were related not only to different strategies of treatment but also to differences in the prevalence and level of important prognostic factors (for example, case mix) and other factors such a the time delay from transient ischaemic attack to entry into the study and the play of chance. The implications for purchasers of health care are that they cannot rely solely on non-randomised comparisons of outcome of patients treated in competing units as a measure of the quality of care (which has only rather modest effects) without accounting for other factors that may influence outcome such as the nature of the illness, the case mix, observer bias, and the play of chance.
在同一国家，几乎在同一时间，采用相同方法对三组大量短暂性脑缺血发作患者进行了研究，并对其结果进行了比较，发现彼此差异很大。结果的差异不仅与不同的治疗策略有关，还与重要预后因素（如病例组合）的患病率和水平差异以及其他因素有关，如从短暂性脑缺血发作到进入研究的时间延迟和机遇因素。这对医疗保健购买者的启示是，他们不能仅仅依靠对在相互竞争的单位接受治疗的患者结果进行非随机比较，以此作为衡量医疗质量的指标（其影响相当有限），而不考虑其他可能影响结果的因素，如疾病性质、病例组合、观察者偏倚和机遇因素。
