在涉及传染病的结局研究中控制疾病严重程度：不同时间点测量的影响
Controlling for severity of illness in outcome studies involving infectious diseases: impact of measurement at different time points.
作者信息
Thom Kerri A, Shardell Michelle D, Osih Regina B, Schweizer Marin L, Furuno Jon P, Perencevich Eli N, McGregor Jessina C, Harris Anthony D
机构信息
Department of Epidemiology and Preventive Medicine, University of Maryland School of Medicine, Baltimore, Maryland 21201, USA.
出版信息
Infect Control Hosp Epidemiol. 2008 Nov;29(11):1048-53. doi: 10.1086/591453.
BACKGROUND
Severity of illness is an important confounder in outcome studies involving infectious diseases. However, it is unclear whether the time at which severity of illness is measured is important.
METHODS
We performed a retrospective study of 328 episodes of gram-negative bacteremia in adult patients to assess the impact of the time of measurement of severity of illness on the association between empirical antimicrobial therapy received and in-hospital mortality. Using a modified Acute Physiology Score (APS), severity of illness was measured at 2 time points: (1) hospital admission and (2) 24 hours before the first culture-positive blood sample was collected. Multivariate logistic regression was used to estimate the impact of adjusting for the APS on the relationship between empirical therapy received (ie, the exposure) and in-hospital mortality (ie, the outcome).
RESULTS
The mean APS (+/- standard deviation) of patients with bacteremia increased during their hospital stay (from 19.2 +/- 11.6 at admission to 24.2 +/- 13.6 at the second time point; P < .01). When examining the association between empirical antimicrobial therapy received and in-hospital mortality, and controlling for the APS, there was a trend toward a decreased impact of appropriate therapy received on in-hospital mortality. The unadjusted odds ratio (OR) for the association between appropriate therapy received and in-hospital mortality was 0.83 (95% confidence interval [CI], 0.51-1.34). After controlling for the APS at admission, this association was attenuated (OR, 0.94 [95% CI, 0.57-1.55]), and when a change in the APS was also included in the multivariate logistic regression model, the association was further attenuated (OR, 0.99 [95% CI, 0.58-1.69]).
CONCLUSIONS
The magnitude of the association between appropriate antimicrobial therapy received and in-hospital mortality among patients with gram-negative bacteremia was sensitive to the timing of adjustment for severity of illness.
背景
疾病严重程度是涉及传染病的结局研究中的一个重要混杂因素。然而，疾病严重程度的测量时间是否重要尚不清楚。
方法
我们对成年患者的328例革兰阴性菌血症发作进行了一项回顾性研究，以评估疾病严重程度的测量时间对接受的经验性抗菌治疗与住院死亡率之间关联的影响。使用改良的急性生理学评分（APS），在两个时间点测量疾病严重程度：（1）入院时和（2）采集第一份培养阳性血样前24小时。多因素逻辑回归用于估计调整APS对接受的经验性治疗（即暴露因素）与住院死亡率（即结局）之间关系的影响。
结果
菌血症患者的平均APS（±标准差）在住院期间有所增加（从入院时的19.2±11.6增加到第二个时间点的24.2±13.6；P<.01）。在检查接受的经验性抗菌治疗与住院死亡率之间的关联并控制APS时，接受适当治疗对住院死亡率的影响有降低的趋势。接受适当治疗与住院死亡率之间关联的未调整比值比（OR）为0.83（95%置信区间[CI]，0.51-1.34）。在控制入院时的APS后，这种关联减弱（OR，0.94[95%CI，0.57-1.55]），当APS的变化也纳入多因素逻辑回归模型时，这种关联进一步减弱（OR，0.99[95%CI，0.58-1.69]）。
结论
革兰阴性菌血症患者接受适当抗菌治疗与住院死亡率之间关联的大小对疾病严重程度调整的时间敏感。
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