Predictive Value of C-Reactive Protein for Major Complications after Major Abdominal Surgery: A Systematic Review and Pooled-Analysis

Background
Early diagnosis and treatment of complications after major abdominal surgery can decrease associated morbidity and mortality. Postoperative CRP levels have shown a strong correlation with complications. Aim of this systematic review and pooled-analysis was to assess postoperative values of CRP as a marker for major complications and construct a prediction model.
Study design
A systematic review was performed for CRP levels as a predictor for complications after major abdominal surgery (MAS). Raw data was obtained from seven studies, including 1427 patients. A logit regression model assessed the probability of major complications as a function of CRP levels on the third postoperative day. Two practical cut-offs are proposed: an optimal cut-off for safe discharge in a fast track protocol and another for early identification of patients with increased risk for major complications.
Results
A prediction model was calculated for major complications as a function of CRP levels on the third postoperative day. Based on the model several cut-offs for CRP are proposed. For instance, a two cut-off system may be applied, consisting of a safe discharge criterion with CRP levels below 75 mg/L, with a negative predictive value of 97.2%. A second cut-off is set at 215 mg/L (probability 20%) and serves as a predictor of complications, indicating additional CT-scan imaging.
Conclusions
The present study provides insight in the interpretation of CRP levels after major abdominal surgery, proposing a prediction model for major complications as a function of CRP on postoperative day 3. Cut-offs for CRP may be implemented for safe early-discharge in a fast-track protocol and, secondly as a threshold for additional examinations, such as CT-scan imaging, even in absence of clinical signs, to confirm or exclude major complications. The prediction model allows for setting a cut-off at the discretion of individual surgeons or surgical departments.

背景
腹部大手术后并发症的早诊早治可降低相关发病率与死亡率。术后C反应蛋白（CRP）水平与并发症存在显著相关性。本系统综述与合并分析的目的在于评估术后CRP水平作为重大并发症标志物的价值，并构建预测模型。

研究设计
针对CRP水平作为腹部大手术（major abdominal surgery, MAS）后并发症预测因子开展了系统综述。研究从7项原始研究中获取数据，共纳入1427例患者。采用logit回归模型，以术后第3日的CRP水平作为自变量，评估重大并发症的发生概率。本文提出两项实用临界值：其一为快速康复流程中安全出院的最优临界值，其二用于早期识别重大并发症风险升高的患者。

结果
本研究构建了以术后第3日CRP水平为自变量的重大并发症预测模型，并基于该模型提出多项CRP临界值。例如，可采用双临界值体系：其一为CRP＜75 mg/L的安全出院标准，其阴性预测值达97.2%；其二为215 mg/L（对应并发症发生概率20%）的临界值，可作为并发症预测指标，提示需追加CT-scan检查。

结论
本研究阐明了腹部大手术后CRP水平的临床解读思路，提出了以术后第3日CRP水平为自变量的重大并发症预测模型。CRP临界值可应用于快速康复流程中的早期安全出院评估，同时亦可作为额外检查（如CT-scan）的阈值，即使在无临床体征的情况下，也可用于确认或排除重大并发症。该预测模型允许各外科医师或外科科室根据实际情况自行设定临界值。