Ohsfeldt R L, Morrisey M A, Johnson V, Treat R
Lister Hill Center for Health Policy, University of Alabama at Birmingham 35294-2010, USA.
Med Care. 1996 Dec;34(12):1180-7. doi: 10.1097/00005650-199612000-00003.
The authors determine whether assessments of effects of rural emergency medical service (EMS) system characteristics on trauma outcomes (using patient-level data) are significantly biased if the Injury Severity Score (ISS) is not available.
The data are from ambulance trip reports merged with the trauma registry data for the Georgia EMS region VI trauma center hospital, located in Augusta. All 294 trauma patients for the rural counties surrounding Richmond County for the calendar year 1991 who were not dead at the scene and were treated at the trauma center are included. A 20% random sample of trauma patients from Richmond county from May to September 1991 not dead at the scene and treated at the trauma center yielded an additional 96 cases. Excluding 43 patients with missing data yields 347 trauma cases with 18 trauma deaths. A logistic regression model for trauma mortality is estimated using the Revised Trauma Score (RTS), ISS, type of trauma, and patient age (analogous to the standard Trauma Related Injury Severity Score model). The predicted probability of patient mortality from this model is compared with the predicted probability of mortality when the logistic regression model omits ISS. Correlations between the difference in predicted probability (i.e., the error in predicted probability associated with the omitted ISS variable) and EMS system characteristics are determined.
Although ISS adds to the predictive power of the trauma outcome model, the errors in predicted probabilities associated with the omission of ISS generally are small and uncorrelated with patient or EMS system characteristics, with the exception of patient gender.
In rural settings, where a patient's ISS generally is not available, studies of rural EMS system characteristics and trauma outcomes may use RTS, patient age, and type of trauma to control for expected survival. The patient's ISS does not appear to be essential, at least for the rural area analyzed in this study.
作者们探究，如果损伤严重度评分（ISS）不可用，那么对农村紧急医疗服务（EMS）系统特征对创伤结局的影响进行评估（使用患者层面的数据）是否会存在显著偏差。
数据来自与位于奥古斯塔的佐治亚州EMS第六区域创伤中心医院的创伤登记数据合并的救护车行程报告。纳入了1991年日历年里，里士满县周边农村县的所有294例未在现场死亡且在创伤中心接受治疗的创伤患者。从1991年5月至9月在创伤中心接受治疗且未在现场死亡的里士满县创伤患者中抽取20%的随机样本，又得到了96例病例。排除43例数据缺失的患者后，得到347例创伤病例，其中18例创伤死亡。使用修订创伤评分（RTS）、ISS、创伤类型和患者年龄（类似于标准创伤相关损伤严重度评分模型）估计创伤死亡率的逻辑回归模型。将该模型预测的患者死亡概率与逻辑回归模型省略ISS时预测的死亡概率进行比较。确定预测概率差异（即与省略的ISS变量相关的预测概率误差）与EMS系统特征之间的相关性。
尽管ISS增加了创伤结局模型的预测能力，但与省略ISS相关的预测概率误差通常较小，且与患者或EMS系统特征无关，但患者性别除外。
在通常无法获取患者ISS的农村地区，关于农村EMS系统特征和创伤结局的研究可以使用RTS、患者年龄和创伤类型来控制预期生存率。患者的ISS似乎并非必不可少，至少对于本研究分析的农村地区而言如此。
