Kirmani Bilal H, Mazhar Khurum, Saleh Hesham Z, Ward Andrew N, Shaw Matthew, Fabri Brian M, Mark Pullan D
Department of Cardiothoracic Surgery, Liverpool Heart and Chest Hospital, Liverpool, UK.
Interact Cardiovasc Thorac Surg. 2013 Sep;17(3):479-84. doi: 10.1093/icvts/ivt222. Epub 2013 Jun 12.
Deep sternal wound infection (DSWI) is a devastating complication of cardiac surgery, with a historical incidence of 0.4-5%. Predicting which patients are at higher risk of infection may help instituting various preventive measures. Risk calculations for mortality have been used as surrogates to estimate the risk of deep sternal wound infection, with limited success. The Society of Thoracic Surgeons (STS) 2008 Risk Calculator modelled the risk of DSWI for cardiac surgical patients, but it has not been validated since its publication. We sought to assess the external validity of the STS-estimated risk of DSWI in a United Kingdom (UK) population.
Using our prospectively captured database, we retrospectively calculated the risk of DSWI for 14 036 patients undergoing valve, coronary artery bypass grafts or combined procedures between February 2001 and March 2010. DSWI was identified according to the Centre for Disease Control and Prevention definition. The receiver operator characteristic (ROC) curve was employed to test the performance of the model using the area under the ROC curve (AUROC). The calibration of the model was interrogated using the Hosmer-Lemeshow test for Goodness of Fit.
A total of 135 (0.95%) patients developed DSWI. Although there was a statistically significant difference in the calculated risk of patients who contracted DSWI (0.44% ± 0.01) vs those who did not (0.28% ± 0.00, P < 0.0001), the AUROC of 0.699 (95% confidence interval: 0.6522-0.7414) denoted a modest discriminatory power, with the Hosmer-Lemeshow Goodness of Fit statistic (P < 0.001) suggesting poor calibration. A risk-adjusted modifier improved the calibration (P = 0.08).
The STS risk calculator lacks adequate discriminatory power for estimating the isolated risk of developing deep sternal wound infection in a UK population. The discrimination is similar to the tool's validation c-statistic and may have a place in an integrated calculator.
深部胸骨伤口感染（DSWI）是心脏手术的一种严重并发症，历史发生率为0.4%-5%。预测哪些患者感染风险较高可能有助于采取各种预防措施。死亡率风险计算已被用作估计深部胸骨伤口感染风险的替代指标，但成效有限。胸外科医师协会（STS）2008年风险计算器对心脏手术患者的DSWI风险进行了建模，但自发布以来尚未得到验证。我们试图评估STS估计的DSWI风险在英国人群中的外部有效性。
利用我们前瞻性收集的数据库，我们回顾性计算了2001年2月至2010年3月期间接受瓣膜置换、冠状动脉旁路移植术或联合手术的14036例患者的DSWI风险。根据疾病控制与预防中心的定义确定DSWI。采用受试者操作特征（ROC）曲线，利用ROC曲线下面积（AUROC）来测试模型的性能。使用Hosmer-Lemeshow拟合优度检验对模型的校准进行检验。
共有135例（0.95%）患者发生DSWI。虽然发生DSWI的患者计算出的风险（0.44%±0.01）与未发生DSWI的患者（0.28%±0.00，P<0.0001）在统计学上有显著差异，但AUROC为0.699（95%置信区间：0.6522-0.7414）表明其鉴别能力一般，Hosmer-Lemeshow拟合优度统计量（P<0.001）表明校准效果较差。风险调整修饰符改善了校准（P=0.08）。
STS风险计算器在估计英国人群发生深部胸骨伤口感染的单独风险方面缺乏足够的鉴别能力。其鉴别能力与该工具的验证c统计量相似，可能在综合计算器中有一席之地。
