前降钙素原、C-反应蛋白和临床肺部感染评分对呼吸机相关肺炎诊断的意义

Role of Procalcitonin, C-reactive protein and Clinical Pulmonary Infection Score in Diagnosing Ventilator-associated Pneumonia

【目的】探讨前降钙素原(PCT)、C-反应蛋白(CRP)和简化临床肺部感染评分(CPIS)对呼吸机相关肺炎(VAP)的诊断效能、相关性以及联合使用的临床诊断价值。【方法】选择广州中山大学附属第一医院重症监护病房(ICU)且疑诊为VAP的成人患者纳入此前瞻性诊断试验,监测入住ICU或气管插管当日以及疑诊VAP当日的PCT、CRP,计算急性生理学和慢性健康状况评分Ⅱ(APACHEⅡ)、序贯器官功能障碍评分(SOFA)和简化CPIS评分,以后每日计算简化的CPIS评分,每48h复查PCT、CRP,收集支气管灌洗物,直至试验结束。结束后计算PCT、CRP、简化CPIS诊断VAP的敏感性、特异性、阳性预测值、阴性预测值,绘制上述指标诊断VAP的受试者工作曲线(ROC)并计算曲线下面积(AUC),根据敏感性、特异性的最佳比值来确定诊断的最佳阈值。【结果】筛选459例患者进入随访流程,最终符合条件者30例,17例通过微生物学证据确诊VAP,13例临床上达到疑诊标准但缺乏微生物学证据而未确诊。PCT、CRP、CPIS诊断VAP的AUC值分别为0.735(95%CI:0.536-0.934),0.599(95%CI:0.361-0.838)及0.809(95%CI:0.641-0.976)。PCT以0.685 ng/mL为阈值,诊断敏感性和特异性分别为76.5%和62.5%;CRP以53.65 mg/L为阈值,诊断敏感性和特异性分别为52.9%和62.5%;简化CPIS以6分为阈值,诊断敏感性和特异性分别为60.5%和92%。PCT≥0.685 ng/mL联合简化CPIS≥6分诊断VAP,敏感性和特异性分别为70.6和100%。【结论】单独使用CRP检测对VAP早期诊断无明显价值;单独使用PCT检测对VAP早期诊断具有一定价值;单独使用简化CPIS进行VAP早期诊断准确性较好;CRP、PCT和简化CPIS评分之间均无显著相关性;简化CPIS评分联合PCT检测有助于提高VAP早期诊断特异性,且敏感性并未降低。

[Objective] To investigate the diagnosis accuracy,relevance and clinical diagnostic value of combined use of procalcitonin （PCT）,C-reactive protein （CRP） and simplified Clinical Pulmonary Infection Score （CPIS） on ventilator-associated pneumonia （VAP）.[Method] All adult patients,who were admitted into the Department of Intensive Care Unit （ICU） of the First Affiliated Hospital,Sun Yat-Sen University and were clinically developed as suspected VAP patients after 48 h of mechanical ventilation,were enrolled in this prospective diagnostic test.Measurement of PCT and CRP levels,and the calculation of the simplified CPIS,Acute Physiology and Chronic Health Evaluation Ⅱ （APACHE Ⅱ） and Sequential Organ Failure Assessment （SOFA） scores were performed at study entry and on the first day of mechanical ventilation.On the day of VAP suspicion,measurement of PCT,CRP and simplified CPIS levels and cultivation of tracheal aspiration were also performed once every 48-hour till the completion of the test.The simplified CPIS was calculated daily.The sensitivity,specificity and positive and negative predictive values of VAP were determined on the basis of respective calculation of diagnosis of PCT,CRP levels and simplified CPIS at the completion of the test study.Receiver Operating Characteristic （ROC） curve was created and area under curve （AUC） was calculated.The optimal diagnostic cut-off values were determined on the basis of the best sensitivity/specificity ratios.[Result] 459 adult patients mechanically ventilated were included in our test,and 30 patients were eligible finally.Of which 17 patients were microbiologically confirmed as VAP,13 patients became clinically suspected VAP but without microbiologic standard.AUC values of VAP resulted from PCT,CRP and CPIS were 0.735 （95％CI：0.536-0.934）,0.599（95％CI：0.361-0.838） and 0.809 （95％CI：0.641-0.976）,respectively.Using 0.685 ng/mL as the best cutoff,PCT had a 76.5％ sensitivity and a 62.5％ specificity; and using 6 scores as the best cutoff,CPIS had a 60.5％ sensitivity and a 92％ specificity.Based on the serum level of PCT≥ 0.685 ng/mL and CPIS ≥ 6 scores to diagnose VAP,the sensitivity was 70.6％ while specificity was 100％.[Conclusion] Using the serum level of CRP alone has little significance on early VAP diagnosis; using the serum level of PCT alone has certain significance on early VAP diagnosis,and using CPIS for early VAP diagnosis had the best accuracy.There was no outstanding correlation among CRP,PCT and CPIS.Joint use of CPIS and PCT could greatly enhance the specificity of early diagnosis of VAP without lowering its sensitivity.