监测降钙素原与感染细胞在呼吸机相关性肺炎的早期诊断价值

Diagnostic Value of Procalcitonin and Percentage of Infected Cells in Identifying Early Ventilator-associated Pneumonia

目的通过早期监测血降钙素原（PCT）和支气管肺泡灌洗液中感染细胞水平，探讨其在呼吸机相关性肺炎（VAP）早期诊断中的价值。方法采用前瞻性临床研究，以2011年1月1日至2012年6月1日连续收住重症医学科（ICU）接受机械通气超过48h、临床诊断为VAP的患者为观察对象，并排除进入ICU时已存在明确感染以及在观察期间并发肺外器官感染者。监测临床诊断当日患者的咀PCT水平。行支气管肺泡灌洗，支气管肺泡灌洗液涂片经迈格吉染色（MGG），计数100个吞噬细胞内有病原微生物的“感染细胞”百分比（PIC）。将监测结果与最后确诊病例进行统计学分析。结果机械通气／〉48h的421例患者中，共纳入76例研究对象，最后确诊64例，未确诊12例。确诊组在疑诊VAP当日PCT水平为（3．48±1．46）rig／mL，PIC为（3．11±1．47）％，显著高于未确诊组[（1．53±0．60）ng／mL和（1．08±0．29）％，P〈0．05]。监测PCT以2ng／mL、PIC以2％为截断值时诊断VAP的敏感度、特异度分别为78．12％、75．00％及78．12％、91．67％，ROC曲线下面积分别为0．87（95％CI78．9％～95．9％）及0．874（95％CI79．2％～94．9％）。两种方法串联诊断敏感度及特异度分别为97．36％、97．36％，ROC曲线下面积为97．9％。结论在临床诊断的基础上，通过监测PCT与PIC的水平，能早期、快速、便捷诊断VAP，使有效抗生素治疗时间提前，值得临床推广。

Objective To assess the value of procalcitonin （PCT） in serum and percentage of infected cells （PIC） in bronchoalveolar lavage fluid （BALF） for the diagnosis of early ventilator-associated pneumonia （VAP）. Methods A prospective observational study was conducted in a teaching hospital. The patients consecutively admitted to the intensive care unit from January 2011 to June 2012, who received mechanical ventilation for more than 48h and clinically suspected for VAP, were recruited in the study. Patients with infection outside the lungs and previous diagnosed infection were excluded. PCT was detected and bronchoalveolar lavage was performed in the day when VAP was diagnosed. BALF cells were stained by May-Grunwald Giemsa （MGG） for counting 100 phagocytic cells and calculating infected cells （ICs） percentage. Results 76 of all 421 patients were enrolled in this study,64 of which were diagnosed, 12 were under-diagnosed. The PCT [（3.48±1.46） ng/mL vs. （1.53±0.60） ng/mL] and PIC [（3.11 ±1.47 ） % vs. （ 1.08±0. 29） % ] were significant higher in the patients with VAP. The threshold of 2 ng/mL of PCT and 2% of PIC corresponded to sensitivity of 78. 12% and 78.12% ,and specificity of 75.00% and 91.67% , respectively. The area under the receiver operating characteristic （ROC） curve was 0. 87 （95% CI 78.9%-95.9% ） and 0. 874 （95% CI 79. 2%-94. 9% ） , respectively. The area under ROC curve was 0. 979,and the sensitivity was 97.36%, specificity was 97.36% when the two cutoff values were both achieved. Conclusion PCT and PIC are useful markers to diagnose early VAP quickly and conveniently and allow early antibiotic treatment of patients with suspected VAP.