Ratios of observed to expected mortality are affected by differences in case mix and quality of care
Ratios of observed to expected mortality are affected by differences in case mix and quality of care
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DOI：
10.1007/s001340000638
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发表时间：
2000-10-01
影响因子：
38.9
通讯作者：
Le Gall, JR
中科院分区：
文献类型：
--
作者：
Metnitz, PGH;Lang, T;Le Gall, JR
目的：验证简化急性生理学评分II(SAPS II)的最新定制版本SAPS II-AM在更大的奥地利重症监护患者队列中的有效性，并评估定制过程对观察死亡率与预期死亡率的影响。设计：前瞻性多中心队列研究。患者和环境：在奥地利的13个成人内科、外科和混合型重症监护病房(ICU)连续入院的2901名患者。测量和结果：将数据库随机分为发展样本(n=1450)和验证样本(n=1451)，采用Logistic回归建立新模型(SAPS II-AM2)。然后通过校准、辨别和O/E比的方法对原始的SAPS II、SAPS II-AM和新开发的SAPS II-AM2进行了比较。计算定制前后O/E比率的差异(DeltaO/E)。Hosmer-Lemesshow对CAP的拟合优度(H)和(C)Over CAP的统计数据显示，数据库中对原始SAPS II的校准很差。新模型SAPS II-AM2比SAPS II-AM表现更好，在验证数据集上表现出色。然而，平均O/E比值在不同的诊断类别之间差异很大(SAPS II的范围为0.55-1.05)。此外，13个ICU的DeltaO/E在-3.6%到+25%之间。结论：目前的严重程度评分系统，如SAPS II，由于没有衡量(和调整)构成病例组合的深层部分而受到限制。因此，患者特征(已知和未知)分布的变化会影响预后的准确性。第一级定制不能解决所有这些问题。因此，使用O/E比率进行护理质量比较时，必须在使用这些数据时非常关键，并应寻找可能的混杂因素。在校准不令人满意的情况下，定制疾病严重程度模型作为质量控制的辅助工具可能是有用的。
Objectives: To validate SAPS II-AM, a recently customized version of the Simplified Acute Physiology Score II (SAPS II) in a larger cohort of Austrian intensive care patients and to evaluate the effect of the customization process on the ratio of observed to expected mortality.Design: Prospective, multicentric cohort study.Patients and setting: A total of 2901 patients consecutively admitted to 13 adult medical, surgical, and mixed intensive care units (ICUs) in Austria.Measurements and results: After the database was divided randomly into a development sample (n = 1450) and a validation sample (n = 1451), logistic regression was used to develop a new model (SAPS II-AM2). The original SAPS II, the SAPS II-AM, and the newly developed SAPS II-AM2 were then compared by means of calibration, discrimination and O/E ratios. Differences in O/E ratios before and after customization (DeltaO/E) were calculated. The Hosmer-Lemeshow goodness-of-fit (H) over cap and (C) over cap statistics revealed poor calibration of the original SAPS II on the database. The new model, SAPS II-AM2, performed better than the SAPS II-AM and excellent in the validation data set. However, mean O/E ratios varied widely among diagnostic categories (range 0.55-1.05 for the SAPS II). Moreover, the DeltaO/E of the 13 ICUs ranged from -3.6 % to +25 %.Conclusions: Today's severity scoring systems, such as the SAPS II, are limited by not measuring (and adjusting for) a profound part of what constitutes case mix. Changes in the distribution of patient characteristics (known and unknown) therefore affect prognostic accuracy. First-level customization was not able to solve all these problems. Using O/E ratios for quality of care comparisons one must therefore be critical when using these data and should search for possible confounding factors. In the case of unsatisfactory calibration, customized severity of illness models may be useful as an adjunct for quality control.